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Emcotec Powerbox vs. Powerbus Pro

Old 03-17-2004, 07:43 PM
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Kris^
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Default Emcotec Powerbox vs. Powerbus Pro

Please NOTE: This is a comparison betweent he Powerbox 40/24 unit (NOT the powerbuss pro) and the Emcotec DPSI RV LDO 12-channel unit. This post has been edited to reflect this correction.


I just installed one of the new Emcotec DPSI RV "LDO" powerboxes in my 40% Composite-Arf. In my OTHER 40% plane I have the "Powerbox 40/24". the Emcotec is sold by DA, the Powerbox by Aircraft International, Duralite, and several other sources. In the next few weeks I'll be going over them with a fine-toothed digital oscilloscope, looking at how they handle the rigors of flying, comparing features, and generally thrashing them as hard as possible so I can make an informed comparison of the two units.

For starters, though .. here's a few items to compare:

The Emcotec, with electronic switch, lists for $329 . .The Powerbox 40/24, for 250 or so, but you have to buy a $75 switch package, so the prices are about the same.

The Powerbox will handle 4 servos/channel for 6 channels. . the Emcotec will handle 6 channels with 4 servos, 4 with 2 servos, and 2 with a single servo each.

Both are rated at 40-50 Amps constant current.

Both "equalize" the battery packs voltage, efectively draining the packs charge at an equalized rate so that both packs are within .05 volts of eachother at all times.

The Powerbox has an LED voltage indicator for each battery, the Emcotec does not

The Emcotec is adjustable from 4.5-6 volts output, the Powerbox stabilizes voltage to the receiver only at 4.8-5 volts, and regulates power to the servos at 6 volts.

Both electronically isolate signal to the servos preventing feedback interference form reaching the receiver or other servos.

The Powerbox is an "open circuit" unit, with the circuitry open to outside contamination, the Emcotec is a semi-sealed unit, that has all the circuitry inside a sealed casing, except for the semi-exposed servo lead ports.

The Powerbox has the receiver leads hard-soldered to the motherboard, while the Emcotec uses plug-in dual-servo leads for this purpose. The leads, all 12 of them, are supplied with the unit.

The Powerbox sellers claim it is necessary for the circuitry to be open to airflow for cooling of the regulator circuits, the Emcotec suppliers claim that this is not needed and the casing acts as a heat sink to slough off excess heat.

There will, of course, be supporters and detractors in each units corner. I've "heard" a lot of noise out of the Powerbox camp, but little out of the Emcotec side. To me, they both seem like good units, which is why I intend to go through them, comparing feature for feature, and circuit and signal purity to see which one comes out on top.

Suggestions for tests, comments from other people using either unit, and any problems encountered with either unit are, of course, welcome.
Old 03-17-2004, 09:58 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Sounds good. You always like testing stuff don't you Kris?
Old 03-17-2004, 10:26 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Just call me the Mad Scientist your first grade teacher warned you about. . .
Old 03-17-2004, 10:34 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Sounds good to me. How about first showing a picture of both units installed in the aircraft? Getting an idea of how each one needs to be set-up and the space required?[8D]
Old 03-17-2004, 10:48 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

I'll have pics tomorrow. I'm in the middle of repairing the gear plate in my 28 lbs 40% plane (oopsie. . deadstick in a heavy wind, from a TR at 35 feet. . actually managed to get it down soft), and am adding the EMcotec setup at the same time. I'll get pics of both setups and post them tomorrow.
Old 03-17-2004, 11:49 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Kris

Based on your descriptions, I’m a little confused here; maybe you made a boo-boo or have the original Modelbau PowerBox 40/24 not the latest version… It sounds like you have an Emcotec DPSI RV Mini (LDO), no?

“The Powerbuspro will handle 4 servos/channel for 6 channels. . the Emcotec will handle 6 channels with 4 servos, 4 with 2 servos, and 2 with a single servo each.”
The PowerBox Pro and Emcotec specifications I have do not correspond with your statement above.

The PowerBox offers seven amplified channels with four channels providing three servo ports and three channel providing four ports. Unless you have an earlier model Pro unit.

The Emcotec Mini RV offers five amplified isolated channels with three channels providing two servo ports and two channels providing single ports.

The "Mini RV" cannot support 40-50 amps (specs say 14amp). The PowerBox is rated at 40amps.

There are many features of each unit that are significant and not mentioned thus far.

The PowerBox Pro was designed for small to large models with a servo load of 24 units currently via seven channels, (previously six channels). Lithium battery technology is not supported with this model (inline regulators can be used). Additional channels are supported through the RX. This is not Modelbau’s top of the line model and does not represent comparable features to the Emcotec RV series. The previously offered Emcotec DPSI 2001 draws a closer comparison unit to unit.

The Emcotec RV’s incorporate onboard voltage regulators supporting all battery technologies with user defined output parameters to the servo buss. Together with audible intelligent voltage monitoring alerts and provides service ports to read pack voltages.

The Emcotec RV offers twelve amplified isolated channels with four single ports channels, two; two port channels and six four port channels.

The "Mini RV" was designed for small models with lower power demands carrying eight servos through the device and two additional channels via the RX while the "RV" is designed for full house models with as many as thirty-two servos.

I am also using the Emcotec RV unit and a Modelbau PowerBox 40/24 Duralite Plus unit. I have yet to shake them out completely but thus far see no problems. These units are a good head to head match, IMO for our comparisons. I'm using Lithium power batteries with a higher servo counts than are required of your highly modified lightweight 40% models.
Old 03-18-2004, 07:09 AM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Uh, Michael, I am using the Powerbox 40/24 (may have misstated the actual name, sorry) . . that I got last year at Joe Nall, and cost me over $375 (since it was sold to me for EUROS, not DOLLARS), and the Emcotec DPSI RV LDO units, NOT the ones you specified. This is a direct test between COMPARABLY PRICED units.

My specifications are taken off the pamphlets for each unit. I'm using NiMH packs in each plane. . 2100's in the one with the Emcotec, 2700's in the Powerbox plane. As you stated, a good head-head comparison. I'll be sure to edit my first post to reflect the proper name for the powerbox.
Old 03-18-2004, 04:12 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Kris quick question, are these busses really needed if you are using 2 rx's in your plane? Just sounds like more points to fail. I subscribe to the KISS theory. The 2 SS apply to me!
Old 03-18-2004, 05:36 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Rtk . .as in everything else in this hobby . .IT DEPENDS. . .

Consider this. .I usually run an external buss strip for power, and all the positive and negative leads for all the servos, as well as two leads for each receiver (redundant power) attach to these strips. . It's dirt simple, not too heavy, inexpensive as can be (about $3 for the strip, and another $25 in extensions for the servo wiring to plug into), ultra reliable, and capable of handling over 100 amps of current, or enough to fry a 14 gauge battery wire.

BUT, what it does NOT do is give me voltage regulation at a set level for more consistent operation of the servos and more accurate flying, "balance" two battery packs so that they discharge at the same rate for more even drain on the packs, filter and isolate each servos wiring from every other servos wiring, amplfy the position signal to the servo, give me an indication of the voltage levels left in the battery packs, or isolate any number of receivers from both eachother and the servos.

Now, these units were originally dsigned with Turbines ( and their horrible RF interference problems) in mind, to prevent interference feedback, and make things work better, as well as to ensure a regulated, filtered, and isolated voltage and signal for every servo in the plane. I've had instances with a "dumb" external power buss setup where one servo glitched bad enough to almost lockout the entire plane, all due to a bad amplifier. These units prevent that from happening. . they also isolate any shorts or other types of electrical glitches form getting back to the reeceivers.

I will never claim that these units are THE fix for whatever ails your planes radio system, but they do a lot of things to help out, and give your system every last chance possible to keep working properly. There are "ways" to do this without these units, but when you weigh the complexity of doing this, with the convenience these units offer, as well as the tremendous boost in consistency and safety they provide, I'd say they would be an accepted "PLUS" for any installation. I wouldn't be looking them over and evaluating them if I thought they were going to give less than optimal results to my testing. And I surely would not buy one if I thought it had no promise. So, I'm gonna look them over. . very well, and give as impartial a report as possible. . some people may not like the results of what I find. . others will, no doubt, be very pleased. But, after all, this is only a hobby, and these units are just another facet in that hobby.

What people will always have to remember is that these units will NOT solve their problems for them, and there is no substitute for a properly laid out and prepared basic installation of radio gear. These units will help with consistency, safety, and with the longevity of stressed parts, such as servos, and in the long run may prove to be very beneficial. Time will tell.
Old 03-18-2004, 07:08 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

It would be nice if somebody would incoporate "Matchbox" type of controls for setting up multiple servos with one of these units. The radio companies could also incorporate that feature into the RXs. Better yet, how about a programable unit that has the controls onboard or uses an outboard device to program the settings. With todays electronics it would not be that expensive. Hey, maybe I should develop, market, and "patent" the concept. Anyway, these units offer some real benefits, but none ahve all that advanced models require. It would be nice to have a"one device does it all" product that is reasonably priced. That way we only need "the device" plus the RX and servos.
Old 03-18-2004, 08:00 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

How about incorporating the receiver right inside "The device" It would mean a lot less external wiring, and the fully logical servo adjustment interface could easily be incorporated right on board.
Old 03-18-2004, 08:36 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Okay, time for some installation pictures.

Photos here are of the Emcotec unit. Note the clean installation possible with the servo leads coming out the sides of the unit, how everything seems to "Fit" the airframe, and how there is plenty of room. the power leads and switch plug go in one end, the receiver leads go in the other, and the servo leads come out the sides. There is an airgap of about 3/8" between the Emcotec unit and the mounting frame, and the frame is about 1.25" tall overall, giving me a place to install the battery packs underneath the Emcotec.

I'll have details of how the unit works and some of it's features later.

Pic one shows a long view from behind the pilot figure, of the installation

Pic two shows the Receiver and leads to it

Pic three shows the power, electronic switch and servo leads along one side of the unit

Pic 4 shows the airgaps under the unit, as well as the batteries plainly visible underneath it.
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Old 03-18-2004, 08:41 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Now the installation of the Powerbox 40/24 unit. The powerbox itself is more compact, but the way the leads are routed makes it more difficult to get a "clean" looking installation, especially with a 10-15 servo setup and a single lead for each servo. Yes, somewhere in there is a powerbox, receiver, and the power wires from the switches. I'm sure the installation would look much neater if I put it on the floor of the plane in the same manner I mounted the Emcotec. In this plane, however, since it's a 40% Composite ARf (normal weight layup) powered by the ultra-lightweight BME110, I needed to shift the weight as far forward as possible. To that end the Powerbox was mounted on the wing tube sleeve, the batteries in the forward part of the motorbox, and even the receiver as far forward as accessibility and space would allow. It made for a rather "tight" installation.

I want everyone to know that these pictures were taken in the middle of a mild drizzle, as I pulled the plane out of my van, removed the canopy, took some quick shots, and then put everything back away. The things I do for this hobby ! ! !


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Old 03-18-2004, 11:02 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Well, when you put it that way, it is hard to disagree. Now you have me interested in you review! March on!
Old 03-19-2004, 12:57 AM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Actually, there is a new Duralite Powerbox coming out called the Champion which will include build in matchbox devices. So its really just getting more and more features. However I know this wont be cheap[X(]
Old 03-19-2004, 06:49 AM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Okay, time to talk about "technical aspects" of the Powerbox 40-24 units.

You can get 2-3 different versions of this Powerbox 40-24 piece, the "Professional" which lists for $225 from Aircraft International WITHOUT the required dual external switches (for an additional $75), the "Competition" version which handles 7 channels but still only 24 separate servo connections, and the "Competition-Lithium" version which is basically the same unit being sold by Duralite. Both of the "Competition" units sell for $325.

First off, the "Professional" unit, which is the same as the one I have. Power to the unit is through two external 20 amp switches, that directly switch the battery pack they are attached to. This power is fed to the unit, and DIRECTLY to the servos, with no voltage regulation to the servos (they get whatever the battery is putting out) the voltage IS, however, "balanced" between the two power inputs, with the higher input biased toward to give power, and the lower level input waiting it's turn. This allows both packs to discharge at an equivalent rate. Power to the RECEIVERS, however, is voltage regulated to 5.0 volts, through two 1.5 Amp rated regulators. All servo signal wires are filtered and separate, preventing feedback on the signal wires. This is a decent "Basic" unit, without too much going on besides rudimentary signal amplification to the servos, as well as high-current capable voltage distribution, with a regulated voltage to the receivers. A lot of "feedback" prevention is also provided by using ferrite rings on the receivers pigtails, to suppress rf noise. The voltage indicator LED's are programmed for EITHER 4 OR 5 Cell packs, from the manufacturer. (I've had two of these. . the first one lost one string of LED's due to a circuitry failure inside the unit, the first time I installed it. Aircraft International replaced the unit for free)

The "Competition" units (include lithium version) are a bit more sophisticated, using fixed 6 volt regulators to BOTH Servos and Receivers (so the receivers are sharing power with the servos again, instead of being regulated lower) The switch changes to a single "idiot proof" (safety) switch with recessed buttons, and is "Electronic" The box itself still shows the plugs for the older style direct-voltage inputs from two switches, so maybe Michael Glavin can clarify whether the current actually passes through tis "Electronic" switch, or if the switch controls an electronic switch inside the unit itself.. Channels are upped to 7 channels in-out, with 4 of the channels feeding 3 servos each, and 3 channels feeding 4 servos. Current capacity of the unit is still 40 amps, and amplification/isolation circuitry to the servos is basically the same as for the "Professional" unit, with a re-routing of signals to include a 7th channel. This unit is focussed more toward high-end turbine aircraft, and is touted as such.

Both units come with 5-LED voltage level indicators on the face of the unit, with the "Competition" units featuring a "Low voltage/inflight error" memory so that the user can check the lowest voltage levels during a flight. Both units also have ports for "Low Voltage Warning LED's" to plug into. These LED's undicate when the voltage from the battery packs has dropped a pre-determined "safe" level, and are mounted in an easily visible place on the plane.

Weight of these units is approximately 5 ounces, and they are rather small, measuting about 4" x 3" by less than 1" thick. They come with mounting grommets and instructions (of course), and the low-voltage indicator LED's. The switch setup for the "Professional" unit must be purchased separately ($75), and the single switch for the "Competition" units handles both battery packs (and appears to handle all the current for the unit as well. . up to 40 amps)

A technical breakdown of the Powerbox 40/24 can be found on the Aircraft International website: http://www.aircraftinternational.com/
You will have to go to "Catalog", then click on the "Powerbox" label/icon. The information is in a downloadable file for Adobe.


Next I'll review the basics of the Emcotec box.
Old 03-19-2004, 07:52 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

And now. . a dissertation of the "Technical features" of the Emcotec unit.

The first thing you notice when reading the Emcotec instruction book is that this is a COMPUTERIZED unit, with memory, programming, and a few things going on inside the box. There is a ton of "stuff" programmed into this unit, all controlled by a small 8-bit microprocessor.

First off you have to TELL it what kind of battery packs you are using, so that it will know how to react to the packs voltage levels. This is accomplished by letting it "learn" what voltage the packs are (follow the instructions). Then, later on, it will give you audible warnings if you have gotten to a low level of the packs capacity (voltage), if you have gone below a "threshold" voltage with either pack while flying (as during a very heavy load with 3/4 drained packs) or if a fault occured in some way while the switch was on. There are no buttons to push, or lights to observe. . just count the "beeps" and refer to the manual for what fault they indicate. The way I see it. . if the unit is beeping, you have a problem, and it's time to take a look at things. .

Then, there is the adjustable voltage regulator level, 4.8 5.2, 5.5 or 6 volts are all set by using shorting strips on two small plugs (as per the instructions). This voltage level is for both the recievers AND servos, and micro-processor controlled.

Next is the LDO feature. LDO stands for "Low Drop Out", and refers to the design of the voltage regulators that gives only .3 volts of "dropout" between the input voltage and the actual regulated voltage, whereas other regulator designs can take .7-1.5 volts. An example of this would be using a 5-cell NiMH pack (As I do). Fully charged I'd have 6.8-7.1 volts or so, but with a standard dropout regulator, I could expect to see less than 6 volts if I went much below 6.6 volts. With the LDO circuitry, the voltage will stay stable down to about 6.25 volts, if the unit is set for 6 volts. Emcotec recommends 5.5 volts for the setting with 5-cell packs, and claims the performance difference is minimal. BUT, you know how modelers are. . I set it for 6 volts and left it there.

Then there is the "Electronic" switch. Basically, the switch carries ZERO current. . the batteries feed directly into the box, and the switch energizes/de-energizes the voltage regulator circuitry. The switch uses a "logic pin". Slipped intot he black hole, the unit is off. . .remove the pin from the hole and the power is kept OFF until the pin is re-inserted into t he RED hole. The same is true going the other way . .If, by chance, the pin falls out of the Red hole while you are flying, UNLESS it is re-inserted into the black hole the unit remains ON. Basically, the pin insertion sets a logic HI, or logic LOW, enabling the computer inside the Emcotec box to either supply power or shut the power off.

The unit is semi-sealed, with only pins for the connectors exposed. The entire casing for the unit is a heat sink, to slough off heat buildup from current and voltage regulation. It's advised to NOT place receivers or other items on top of the Emcotec box, and to give at least 3/8" clearance on top and bottom for air to circulate around the unit and provide cooling. I left the Emcotec box on for an hour with all servos running (about 1.5-2 amps draw maximum), and the box never got warm to the touch. When under flight loads, though this will change. Emcotec also advises to NOT rigidly mount the unit, but to let it "float" if possible. I used 8 soft rubber grommets and #8 decking screws to mount the unit to the mounting bracket I made.

Every signal wire is amplified to the servos, and every channel is isolated from the others, so no feedback is (theoretically) possible.

The Emcotec unit can handle 6 channels with 4 servos each, 2 channels with 2 servos each, and 4 channels with 1 each, for a combined total of up to 32 servos on individual plugs.

Maximum sustained current draw is rated at: 5.5 volts, 6-cells, 8 amps for 15 minutes continuous. . . .5.5 volts setting, 6 cells, 56 amps for 10 seconds. Lower cell count, and higher regulator voltage (say. . 5 cells and 6 volts setting) will increase the time-span for these loads, because the voltage regulators will not be working as hard. I imagine that on 5-cells, and set for 6 volts, you could run 12-15 amps continuous for 15 minutes and probably get away with 56 amps for 20 seconds. No one is EVER going to load this unit that hard, though.

Lastly, the unit weighs about 8 ounces, including switch. It comes with ALL receiver-box connector wires (12 pigtails), the switch, and two plugs for connecting the wires form the batteries. What it does NOT come with, however, are mounting grommets and screws, which would be a nice touch.

This unit is designed to work well with any 5-cell NiCad or NiMH pack, and the dual cell Lithium packs now available, OR equivalent voltage Nicad/NiMH packs of 6 or 7 cell count. Battery packs of less than 6 volt capacity (such as 4-cell NiCad packs) are not listed as compatible with this unit. . and no voltage regulation will take place because the packs have insufficient voltage capacity.

Here is a website address for the Emcotec series of products in ENGLISH: http://www.rc-electronic.com/html/en.../englisch.html
Old 03-19-2004, 09:04 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

ORIGINAL: Kris^

Okay, time to talk about "technical aspects" of the Powerbox 40-24 units.

Power to the unit is through two external 20 amp switches, that directly switch the battery pack they are attached to. This power is fed to the unit, and DIRECTLY to the servos, with no voltage regulation to the servos (they get whatever the battery is putting out) the voltage IS, however, "balanced" between the two power inputs, with the higher input biased toward to give power, and the lower level input waiting it's turn. This allows both packs to discharge at an equivalent rate.
I like the data on the Professional, although I’m no expert. It all sounds right less the power bias balancing. How is this accomplished? The PowerBox Pro is using the Dual-Power-Control with a dual Schottky diode component in series to the servo buss. Electrons seek the path of least resistance <-, If we assume the switches, diodes and accompanying wiring offers nearly the same resistance the only other factors will be the batteries and or cells combined impedance, or more specifically impedance under load…

Power Routing: Professional

Battery Packs -> On/Off switches -> Dual-Power Control or dual Schottky diode -> servo buss -> servo ports. The only balancing I can perceive is the normal flow of power under the least resistance and highest voltage until such time both batteries are mono-mono. This is more likely to occur under load, unless of course all is equally matched going in…

I would be willing to align myself with the idea that this system offers a better method to maintain balanced power results than the more sophisticated switched-regulated-diode-buss system in play with the PowerBox Compettion and the like.

The "Competition" units (include lithium version) are a bit more sophisticated, using fixed 6 volt regulators to BOTH Servos and Receivers (so the receivers are sharing power with the servos again, instead of being regulated lower) The switch changes to a single "idiot proof" (safety) switch with recessed buttons, and is "Electronic" The box itself still shows the plugs for the older style direct-voltage inputs from two switches, so maybe Michael Glavin can clarify whether the current actually passes through tis "Electronic" switch, or if the switch controls an electronic switch inside the unit itself.
Power Routing: Competition, Duralite Plus and I assume the new Champion

Battery packs -> electronic switches -> regulators -> diodes -> servo buss -> servo ports

The PowerMOSFet electronic switches are remotely operated by the “Sensor” switch, the micro controller will switch on the system when it awakes from sleep mode. These units utilize three power semi-conductors. This system will more likely than not create an unbalanced Conundrum. Typically one regulators output voltage is slightly different (approx. 2%). Therefore the balance between the batteries is affected. The voltage regulator maintaining the higher of the two output voltages will be loaded from the flight system. The second regulator will be loaded less (depending on the current). This means, you’ll never use the full capacity of both batteries. One battery will be depleted earlier than the other in the most cases.
Old 03-19-2004, 09:42 PM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

I imagine that if you used a digital voltage comparator, operating at high frequency, that would monitor the input voltages and "forward bias" power from the stronger pack, instead of an either/or situation, you could closely regulate the voltage level from both packs, thus effecting a "Balance" throughout discharge. I've checked my Powerbus 40-24 inputs from the battery packs after coming off charge. . one pack is always slightly higher than the other, but after 2-3 flights both packs read the same, and this continues right down to my 6.1 vdc bottom limit for the packs. Not having the exact schematics or logic diagrams and flow chart parameters, and not being able to pick the circuit apart, it's kind of hard to refute the MANUFACTURER's claims. This is what is claimed by Herr Deutsch, and what I have actually witnessed through a few discharge cycles at the flying field.

I'm going to do 4-5 flights each with both planes this weekend, and will be doing "Switch on, servoes idling" voltage readings before and after each flight, to track the output voltages of the packs, and see how well they are being regulated by the power boxes. I just hope I can outlast the battery packs.

BTW, I just got off the phone with Gerhard. . the special "Logic" switch for the Competition powerbox units actually carries 100% of the current from the batteries, unlike the switch for the EMcotec, which is a TRUE logic-switch and controls the box itself.
Old 03-19-2004, 10:49 PM
  #20  
mglavin
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Default RE: Emcotec Powerbox vs. Powerbus Pro

ORIGINAL: Kris^

BTW, I just got off the phone with Gerhard. . the special "Logic" switch for the Competition powerbox units actually carries 100% of the current from the batteries, unlike the switch for the EMcotec, which is a TRUE logic-switch and controls the box itself.
Gerhard is misinformed.
Old 03-20-2004, 06:11 PM
  #21  
Kris^
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Agreed, Michael, Gerhard made a boo boo, as looking at the picture of the Powerbox "Competition" unit pictured on the Duralite website distinctly shows a "Logic cable" from t he switch assembly to the powerbox, meaning that the switching and power management are similar to the Emcotec unit.

The attached picture shows what you get when Emcotec says "amplified signal" This picture is of a Fluke 98 digital o-scope screen, showing input/output from the Emcotec unit on the Throttle channel. As you can see the pulse has very little, if any, amplification. The input signal (channel A) is about 1.8 volts in amplitude, and the signal out (Channel B) is 1.9-2 volts, though it's hard to see without a lot of study. This is not a lot of amplification, though the signal is definitely slightly different (note the "noise" spikes and how they do not coincide exactly) showing that it is definitely going through a filter/amplifier of some sort, which nullifies feedback along the signal wire. A straight-through signal would be an exact duplicate of it's partner.

So, yes, the signal goes through a "stage" inside the Emcotec box, that mildly amplifies it and nullifies feedback, though the effect of the amplification, in this instance, is a factor of less than 10%.
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Old 03-22-2004, 06:24 AM
  #22  
Richi-d
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Hi- somebody asked for Matchboxes on a Powerbox - you get it! The new Powerbox Champion has three "Matchboxes" onBoard! you get it here:

www.duraliteplus.com
www.aircraftinternational.com
Old 03-22-2004, 08:46 AM
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Kris^
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Perhaps you would care to provide the exact routing to the information, pictures, and pricing for these units. . .it does not seem to be available at this time.
Old 03-22-2004, 09:55 AM
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Since the wind was up this weekend, and I had to WORK anyway (YUCK .. another ruined weekend) I decided to play with voltage readings and see how things panned out. I'm studying the Emcotec right now, since the plane is still on the bench. I'll get the Powerbox 40/24 in this afternoon and go over it's readings.

I'm using dual 2100 ma NiMH packs (or. . I WAS), using Deans conectors (the super large ones). Voltage drop across the connectors is .001 volts or less, so you know they are doing their job. I started noticing a problem while slammng the sticks around and watching the DC voltage level. The battery packs started with 6.65 volts each, and the output from the Emcotec unit was a steady 6.1 volts with system ON, but no movement.

I've always felt that the best way to see how efficient a planes battery power and wiring are working is to watch the voltage while you hit the Snap button at full rates. This moves all three major controls at the same time, effectively putting maximum load on the battery system. A lot of people forget that the highest current drain form a motor is not while it's moving, but when it's NOT moving, then starts to move. During that very short period the motor basically acts as a dead short while the magnetic windings absorb voltage and turn it into inductence. As soon as a full magnetic field develops, you get a steady amount of "reluctance" (basically, the resistance to current flow through a steady magnetic field. . i.e.. . full charge inductor/winding/transformer), and the amount of current flow is much lower.

As for those silly little 1-amp steady-state voltage "load" boxes. . . at best they are silly, at worst they will give you false confidence that your packs are really working properly. You get the same result by just turning the switch on and seeing what the voltage level is with the servos holding the control surface in place. What you really need is a "snapshot" of the packs under extreme load, to see how well they are reacting to amperage loads 8-10 times their capacity. If you can hit the pack with that sort of load, and realize less than .7-.8 volts of dropout. .THEN your pack is working as it should, and all the cells are operating properly. A 1-amp steady-state load tester will NOT show a cell that is starting to weaken, and which may fail 5 minutes from now. A Snapshot test WILL show this, however, since the marginal cell will cause a higher-than-normal voltage dropout as it goes offline during the snapshot test. People fail to realize that batteries have a "reaction time". . the slower they react, the more marginal they are, and the closer to failure they come. Quick Snapshot tests show these characteristics much better than .5 or 1-amp steady-state testers.

SO, you may not be able to read the current draw directly (its not REALLY necessary either) but you CAN see what that extreme amount of current is doing to your batteries and wiring. In this case, when the servos are not moving, then the Snap button is pushed and all 13 of them start to move at once, you get a REALLY big current spike. I was watching the voltage level of the battery packs, and they would go from 6.6 volts down to less than 5.7 volts, then recover to 6.6 volts when the servos stopped moving. This was read directly off the pack, before any connectors. After about 10 minutes of "snapping" the plane, the packs had depleted to only 6.2 volts, which made me uneasy, and the low point of the voltage spikes had fallen to 5.25-5.3 volts.

Of note, though, the Emcotec box handled things pretty well, and I could not tell when the regulators fell off line and bypassed the voltage that was less than their rating, and the signal trace was very smooth. The output side of the box read a steady 6.1 VDC, but during the "snaps" almost perfectly mirrored voltage readings directly off the battery packs, showing a low voltage point less than .1vdc lower than the reading directly off the batteries.

Given the large voltage "depletion" of the packs, I looked them over. They used 18 gauge wire, were rated at 2100ma, and were less than 6 months old. I had some older packs on the shelf, rated at 2150ma, so I opened them up and got rid of the 18 gauge wire and soldered in some 14 gauge "power wire" used in electric buggy applications, then soldered the wires to new Deans plugs and installed the packs. After 8 hours on .1/C charge I switched the charge rate to 1/20/C, and left them overnight (10 hours), then two hours of "trickle". "Baseline" voltage was 7.05 voltes, one hour after being taken off the charger. Switch on, servos idling, and the voltage dropped to 6.85 volts over a 10 minute "idle" period to scrub off the top-surface of the charge.

Now the "Snapping" began again. . .output from the battery packs never lost more than .5 volts, with a low point of 6.4 volts, and the "idle" voltage level returned to 6.8 volts, during the 5-minutes of snap, snap, snap, snap, snap, probably 100 snaps in a row (this REALLY draws some current, btw). At the same time, voltage from the output side of the Emcotec box showed an Idle level of 6.1 volts, and a fully loaded level of 5.85-5.9 volts, a .2-.25vdc drop under very heavy loads. It's pretty obvious that there is some voltage depletion going through the Emcotec box, but this is to be expected from any electronic unit. I don't consider 1/4 volt, under this sort of extreme loading, to be an issue, and am mildly surprised that it is not a higher dropout. Anytime you ahve a voltage regulator at work, there is going to be a substantial amount of dropout under loads, even if the circuit is bypassing the voltage because it is below the rated output of the circuit.

As for what was happening with the first set of packs? First, the 18 gauge wire was not helping matters. At about 5-8 amps of current 18 gauge wire starts to provide resistance, lowering the available voltage. With each "snap" I was probably pulling 25-30 amps of instantaneous current, if not more, as the servos started moving, then stopped at the end of the travel. I'm of the opniion that the wiring itself was just not up to the task, and provided most of the voltage dropout under heavy loads. As well, the packs had been fast-charged at a .2/c rate for only 4 hours the day before, and not trickled to "balance" the cells, so some of the cells in each pack were probably at a lower capacity level than the others, effectively reducing available power from the packs. A lot of people don't realize that a "balance" period, under trickle charge, of 3-4 hours is almost a necessity to get 100% out of a multi-cell NiCad or NiMH pack, and you can't just slam them on the charger, then yank them off it and put them in a plane right after they finish the charge cycle. This is especially true for "fast charge" rates around .5/C-C1 rates or faster. This is one reason I use a charger than never charges at faster than .2/C rate, and usually leave it to trickle for a few hours before I go flying. I also never "peak" charge. this is just my own technique, as I feel that a full charge cycle at .5 or .1/C rate, then trickle charge, will bring the packs up to full capacity more gently, and ensure a "balanced" pack after the charging cycle is finished. I'm sure Red Scholefield, or some of the other battery "gurus" could write books about this practice.

You know. . you gotta wonder. . .JR "Superswitch" wiring is WHAT gauge?? 20-22, right? And the connectors use those teensy little gold plated plugs 22 gauge "heavy duty" wiring .. and people just plug these things into their planes, directly into the receiver buss land plugs, and EXPECT to fly with no problems. . . you just gotta wonder how much voltage and current this system is actually capable of handling. . Perhaps it's okay for a Pattern sized plane, but when you get up to 30-40% or larger things get marginal REALLY quickly. I have an 80" funfly I'm finishing. . it uses 6 8411 servos and a single 5735 HiTec for the controls. Off a fully charged 2700ma NiMH pack w/14 gauge wiring, I had to run TWO JR Superswitches to the Receiver, otherwise the servos would start getting really sluggish or the receiver would drop out into PCM lock due to low voltage. I installed a single DPDT 20-Amp switch from Radio shack (40 amp capacity), with 3 power pigtails on the output side to the receiver ports, and no more problems. . . .you just gotta wonder how marginal things really are.
Old 03-26-2004, 03:26 PM
  #25  
Richi-d
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Default RE: Emcotec Powerbox vs. Powerbus Pro

Sorry for the delay - I was in France for Parabolic flights
More information about the NEW ONE at the fair in Toledo...

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