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regular voltmeter and onboard?

Old 02-10-2005, 04:48 PM
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cstewa
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Default regular voltmeter and onboard?

hey guys, just getting back into it after8 years.

I can't find my old voltmeter to check my reciever pack at the field. I remember when we used to fly with my dad we never checked them. But we were usually alone in the cowpasture. But at the local club here there are usually people there and I would like to keep a monitor on the reciever pack.

so my questions are?

1. do most of you regularly check you reciever pack at the field? and how often? 3 flights 4 flights or minutes used?

2. Not looking to spend alot of money but what voltmeter is cheap and easy to use? I have a futaba skysport 6channel with standard reciever pack. 600mah. I will be flying a super sporter 60.

3. I have seen these on board flat votmeter things i guess you stick on the side of you fuse? does anyone use these?

thanks
Old 02-10-2005, 04:55 PM
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famousdave
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Default RE: regular voltmeter and onboard?

The on board devices are useless as they don't put a load on the batteries.

The best and most cost effective meter you can use is the Hangar 9 load meter. Its about $40 at the LHS, has a universal connector a 0.5 and 1A load capability and a display that reads to 1mV. It also fits in your pocket.

I read mine EVERY flight on my single pack planes, once every few flights on my larger capacity, dual pack planes...

DP
Old 02-10-2005, 05:31 PM
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cstewa
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Default RE: regular voltmeter and onboard?

is this the one you are speaking of
http://www.horizonhobby.com/Shop/ByC...?ProdID=HAN105
Old 02-10-2005, 05:39 PM
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cstewa
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Default RE: regular voltmeter and onboard?

oops...I think I found it.
http://www.horizonhobby.com/Shop/ByC...?ProdID=HAN171

does the universal connector work with my futaba sky sport? I know...I know it says universal but does that mean universal as well...
Old 02-10-2005, 06:21 PM
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famousdave
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Default RE: regular voltmeter and onboard?

That's the one... it works with Futaba J connectors.. if your radio has the J connector (I thought all FUT systems do) then it will work fine out of the box.. ! Of course it also works with JR, Airtronics, etc too ..

DP
Old 02-10-2005, 07:57 PM
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BillS
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Default RE: regular voltmeter and onboard?

You can buy a digital voltmeter at Harbor Freight for $3.95 and a load resister at Radio Shack.

Bill S
Old 02-10-2005, 09:23 PM
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JPMacG
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Default RE: regular voltmeter and onboard?

Ditto the cheap digital multimeter and resistor. No need to buy the expensive Hobbico or Hanger 9 meters in my opinion. The multimeter can also be used to check continuity, measure dc and ac voltage and current. It's much more versatile than the specialty RC meters.

The little on-board flat thing you refer to is probably a VoltWatch. I for one find them very useful, however, they cannot be used in the same manner as a loaded meter. You need to wiggle the servos and see how the monitor responds. It actually can give you more information than the loaded meter, but again, you must learn how to interpret it.
Old 02-10-2005, 09:54 PM
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Default RE: regular voltmeter and onboard?

It depends if you want a hand made kludge at the field you have to fumble wth or a compact sealed unit that is simple to use and bullet proof.

Yes, there are always ways of doing it cheap. To me $40 for an invaluable tool that I only need to buy once IS cheap.

One can only squeeze a penny so tight - sooner or later Abe Lincoln's gonna SH*T in your pocket.
DP
Old 02-11-2005, 05:38 AM
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Default RE: regular voltmeter and onboard?

Desertpig,
The on board devices are useless as they don't put a load on the batteries.
Not so. If you read it at the end of the flght before the batteries build back a surface charge you get a very good indicator of battery life. Because its reading the actual load that was applied during flight. Not a simualated load. Now if your talking about getting a good indication of battery life "Before" the flight I'd also use a loaded voltmeter.

Speaking of loaded voltmeters.
It depends if you want a hand made kludge at the field you have to fumble wth or a compact sealed unit that is simple to use and bullet proof. Yes, there are always ways of doing it cheap. To me $40 for an invaluable tool that I only need to buy once IS cheap.
However if you've already got digital voltmeters buy a dual banana plug at Radion Shack. Solder a #47 bulb for a 200 mA load across it. plug your Hobbico receiver leads into it and you don't have a kludge it's mall and plugs in. You have an indicating load with an accurate voltmeter for $5.00 plus the price of the Hobbico leads. For me this beats having a $40.00 specific built meter that absolutely useless for anything else.

Just my 2 cents.

John
Old 02-11-2005, 10:23 AM
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famousdave
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Default RE: regular voltmeter and onboard?

I guess it all depends on the application and how much you really want to know about your battery. I have 5 planes, all giant scale 30% +... all on Lithium power. I need a consistent 1A dynamic load, which is what an "active" load places on the pack. A simple resistive load may be fine for one pack type, say NiCads, but wont work very well for a variety of packs like 4 cell, 5, cell, NiMh, Li-Ion, etc. I use the meter for my cars, boats, helis and planes... all on different voltages and battery types! It has paid for itself over and over. The reason that little H9 meter costs what it does is that it provides a 0.5 and 1.0 A load at all common voltages up to 12V using a remedial load circuit - something like a reverse regulator... Its not just a panel meter with a resistor inside.

I at least know that if my pack is at 8.3 volts or 7.9 volts it will hold the load when the meter is connected. That simply won't work with a meter and fixed load (i.e. resistor or light bulb) unless you carry a resistor network or rheostat and just happen to know which value is needed for which voltage. ..

If you look at the pic below, you can see there is a little more to this meter than just the load resistor.. the circuit under the heat sink is the active load.

Anyway, it was just a suggestion. If money is that much of an issue and you are only using a 4-cell NiCad for the rest of your flying days then I guess the meter approach is probably OK...

I tend to heed the old motorcycle racing adage - "if you have a $50 head, its OK to buy a $50 helmet" ...
DP
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Old 02-11-2005, 11:42 AM
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Default RE: regular voltmeter and onboard?

Desertpig,
2. Not looking to spend alot of money but what voltmeter is cheap and easy to use? I have a futaba skysport 6channel with standard reciever pack. 600mah. I will be flying a super sporter 60.
My advice was aimed at flying a Futaba 6 channel and a Super Sportster.

If I was flying Giant Scale I'd put a LM317 with a 1.2 ohm resistor for a 1 amp regulated load switched via a SPDT toggle switch to a 2.4 ohm resistor for a .5 amp regulated load and mount it to a 4 1/2 digit LCD panel display on board with a push button switch to read the loaded values otherwise the voltmeter would read the buss. Cost about $25.00 per plane. I hate forgetting stuff like meters and would rather have them built in.

As far as old motorcycle adages - I replaced my Harley Sturgis this fall with a 102 cu inch Yamaha Road Star. I'm was having lots of fun till the snow hit!

John
Old 02-11-2005, 11:49 AM
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Default RE: regular voltmeter and onboard?

Actually I think I lied. Giant Scale I'd put the voltmeter on the side but I think I'd invest in that new digital recorder from Eagle Systems. It's really nice to see what actually happens in the air. http://www.eagletreesystems.com/

John
Old 02-11-2005, 12:06 PM
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Default RE: regular voltmeter and onboard?

John-

I do whatever it takes to save weight and piling on extra devices like telemetry and tachs, meters, etc.. while handy, adds weight. Oh well.. that's why this is a hobby.. lots a different ways to do things! I don't disagree with your approach.. just different than mine.

I have used the RCATS telemetry system before, it records everything. Very handy when setting up a plane or just testing a design..

So why the Roadstar? Why not a Road Glide or other big hog? I have a significantly hopped 02 road glide that I just love. I swapped with one of my riding friends on a day trip once... I rode the big 'star for about 150 miles.. it was quite nice.. smoother and a lot faster than the Harley, but not as comfy on the long haul.. my back started bothering me due to the seating position. I took my Harley back!

When I want to go fast I have a Ferracci Prepped Ducati 748 SPS! 107 HP and 377 pounds! The only gripe I have with that bike is that a $250 rear tire only lasts me about 500 miles... something about that damn throttle.

DP
Old 02-11-2005, 12:22 PM
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Default RE: regular voltmeter and onboard?

Desertpig,
I do whatever it takes to save weight and piling on extra devices like telemetry and tachs, meters, etc.. while handy, adds weight. Oh well.. that's why this is a hobby.. lots a different ways to do things! I don't disagree with your approach.. just different than mine.
Agreed. There is always a different approach. I just vividly remember a posting by Hangtime concerning a Giant Scale that the battery voltage on the buss came dangerously low and they only way they caught it was with an on board system. Their solution was to use two separate NiMh packs in parallel - half the size of the original, it lowered the internal resistance of the packs and allowed it to supply the peak current necessary for the digital servos with no additional weight. So I think I'd use an onboard monitoring system at least for sorting out a new aircraft.

When I want to go fast I have a Ferracci Prepped Ducati 748 SPS! 107 HP and 377 pounds! The only gripe I have with that bike is that a $250 rear tire only lasts me about 500 miles... damn throttle.
Hot D***! If I was 20 years younger I'd love to ride something like that, actually I'd like to now. Just wouldn't be able to do it justice.

I rode the big 'star for about 150 miles.. it was quite nice.. smoother and a lot faster than the Harley, but not as comfy on the long haul..
On the other hand mine fits me better than the Sturgis did and it's much smoother above 70 mph. I rode it to the airfield and everyone was asking when I was going to get a trailer for it to tow my airplanes with.

John
Old 02-11-2005, 12:26 PM
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Default RE: regular voltmeter and onboard?

Now you know why I'm still flying 120 size planes this year. The wife said I could wait on the 1/3 scale until I got the bike paid off. both put a smile on my face so I don't feel it's any hardship!
Old 02-11-2005, 11:18 PM
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Default RE: regular voltmeter and onboard?

Here is my kluge loaded DMM. The DMM is a cheapie from Harbor Freight. I checked it against my Fluke and its DC voltage is right on. The load is an 18 ohm 2 watt resistor. This gives a current of about 270 mA on a 4.8 V rx pack. The Futaba J connector is from Radial RC and comes with banana plugs that plug into the DMM. The resistor is connected in parallel with the Futaba connector using stackable banana plugs, although it could just as well be soldered directly to the connector's plugs.

Desertpig has a good point regarding the active load. With the resistor the load current is proportional to voltage, so, for example the current would be about 540 mA with a transmitter pack using the same resistor. Transmitters usually have built in meters, so this is not an issue for most of us.

One can make an active load using an LM317 IC (Radio Shack carries them) hooked up as a current regulator. It could be mounted to a small aluminum bar to provide some heat sinking and used in place of the 18 ohm resistor. But unless you want to start a new hobby, that would be a silly use of your time.
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Old 02-12-2005, 07:19 AM
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Default RE: regular voltmeter and onboard?

Hey - How did you get a picture of my voltmeter - Looks exactly like what I cooked up.

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