Cat 1

My Feedback: (1)

Rob,

the only changes I have made are I added an air bleed to get the idle solenoid setting a bit higher up on the curve. And I also added a "heat isolator" made out of Delrin (acetal). Both made the engine run slightly better.

Will document then with a few pics and get you measurements..

Chris

Cat 1

My Feedback: (1)

Rob... found the pics - #55 (0.052" or 1.3mm) hole drilled as in pics for idle improvement - And the heat isolator as shown - Helped hot starting and a bit at idle too I believe.

hmeijdam

Hi folks,
About the latest generation of all-in-one BMP180 (not BMP280) integrated controllers that I made for Bert, there should not be any issues with voltage spikes. They have a built in voltage regulator, to make them HV compliant and then an additional RC (resistor/capacitor) filter to take care of the electromagnetic noise the solenoid will generate. I also clocked the microprocessor at 8MHz instead of 16MHz, so it will continue to work down to 3 Volt.
The BMP180 module has it's own regulator, as it is a 3.3 Volt device.
Anything from a 4.8v NIMH pack to HV (2S Lipo) should work.

The separate pressure module for the LUA script, that Bert was talking about worked with a 16MHz clocked processor, that likes 4.5V minimum. That created some issues when fed from a 4.8V NIMH pack. That's when I decided to clock them at 8MHz moving forward, so they can deal with a lower input voltage
Hans

1967brutus

Thanks, Hans!

cmulder

Could you power the new version with a adjustable power supply?
Then slowely dial down the voltage to see what happens?
There might be a "in between" voltage where some parts still work and other functions quit.

1967brutus

I think Hans did just that, and found no issues. Correct me if I'm wrong, Hans...

hmeijdam

This time I have used a combination of nimh cells and alkaline batteries to get a variety of voltages and not my lab power supply. Though you could do exactly what cmulder suggested if you want to do your own test. I suspect the solenoid will also start to drift, as the speed it opens will degrade below a certain voltage, or even not open at all. But that's Bert's "department".
I have set Brown Out Detection in the microprocessor at 2.7 Volt, so it will reset itself before low voltage flash memory corruption may occur. So the test shouldn't harm anything.

1967brutus

FWIW I have not yet been able to detect any changes in engine behaviour due battery depletion or voltage drop due depletion.

cmulder

While this shows your whole system is working, it does not demonstrate how the seperate components behave undr less then ideal conditions.

For example:
Batteries of the type we use can be defined as a constant voltage source with a resistor in series.
The voltage is the result of the chemical reaction during discharge. The resistance is the result of the material that has already reacted having a higher resistance then the material that has not changed yet.
So when a battery discharges its not the voltage that changs but its internal resistance. This is why batteries have to be tested "under load" so that the voltage drop over the internal resistance is measured to confirm its charge state.
This is verry simplefied explenation just to get the basics explained there is much more going on like temperature.

While the computer part of the system draws a fairly constant current, the moment the solenoid is switched on the current increases.
So the effective battery voltage goes down and will go back up again when the solenoid is turned off again.

Running a engine will only show if there is a big enough problem that affects engine performance enough to be noticeable.

That is why i recomend some more advanced testing

1967brutus

I am a bit confused: if the engine is running, it is running. Mixture is fairly critical, so anomalies show up. I use virtually exclusively single battery set-ups, with one battery (often as small as 2000 mAh) powering RX, Servo's, ignition and fuel system. That is a LOT of variable current draws there in one single system. If it handles that, IMHO that should suffice.
Hans went quite a bit further with his testing, he used batteries of various chemistries and tested several different set-ups hooked to measuring devices. What can I say more?

Glowgeek

I use a single A123 LiFe pack as low as 1100 mah to power everything in my smaller gassers. A single 2300 mah LiFe pack for larger gassers. Dual 2300 mah LiFe packs in 25% and up gassers.

A123 round cells have very low internal resistance, meet the high current demands of strong servos, charge very quickly, have a VERY long lifespan, can be left fully charged without self destructing, hold 90% or more of their charge if left for a year on the shelf and maintain a VERY consistant output voltage. Why anyone would use any other chemistry to power onboard electronics in a gasser completely escapes me.

--ducks and runs for cover--

1967brutus

Because I don't own any A123 cells

Glowgeek

Easily remedied. In the US the premier supplier of A123 round cell LiFe packs is Hangtimes Hobbies. They have an EXCELLENT faq page on the superiority of LiFe technology.

Almost any programmable charger that can charge Lipo packs can also charge Life packs. A simple DIY charge cable made from parts you likely already have lying around is all that's needed. I couldn't afford to swap chemistries in all my planes at once, so I started with my gassers and replaced the others as I could afford.

hmeijdam

When I did my tests I worked from the assumption that the majority of 2.4GHz receivers do not like a voltage of less than 4 Volts. The FRsky X8R for example has a 4-10 Volt operating range.
The Solenoid module will be powered from the receiver, so before someone would power the solenoid driver insufficient, he may already have a problem with his receiver.

Glowgeek

I think the CDI would fail before the RX.

hmeijdam

I thought Bert was more of the exception with his single battery setup and most people use a separate battery for the CDI and an Opto killswitch. But if it is one battery I think you are right with the CDI checking out first.

1967brutus

The older ignitions failed at 4V, and that would be before the FrSky receivers failed. Later ignitions (at least the later ones from RcExl) won't go lower than approx 5,5 V so for a few models I have either changed to a dual battery set-up, OR to 5 cell NiMH single battery and on occasion 2S LiPo with a either a 5V voltage regulator for RX and the ignition unregulated direct from the battery, or a 6V regulator and the ignition fed from there as well.
5S NiMH does make some servo's act a bit weird when the battery is "hot from the charger" but other than that, no issues....

cmulder

I am not aware of any suplyer in the country here who sells a123 cells to consumers.
On the other hand i buy my nimh cells at my local lidl (yes i am cheap) supermarket.
Cycle each cell a few times and the best performing cells end up in reciever packs and the others are for normal "household" use
Got a 30 ish year old Robbe mtc51 charger that charges at about 1/10th C overnight and then pulses to keep them topped up.

If i could get A123 cells at a more reasonable cost then i would use them too but for now the cost of my homemade packs is less then the shipping cost of a pack from mainland Europe.

Also: being able to for a cell to give high current and to be charged fast is a direct result of the internal resistance of the cell.
The voltage drop times the current is the amount of energy (in watts) changed into heat inside the cell.
Heat is what kills a cell so a cell that keeps cool (low internal resistance) will perform better.

cmulder

The kind of voltage variations that can confuse a computer are much "faster" then you can measure with a digital (or analog even) multimeter..
Ony a oscilloscoop will show this

We should not only test wat works but als what causes it to stop working and what symtoms show. That way we can provide proven steps to correct "end user" problems quicker.

1967brutus

I know that... but if experience shows that that does not happen (the processor getting confused), then I am not sure what to test...
I mean, Rob.M had an issue with his RX on/off switch, and it would not show up on his telemetry but it did show up in a "confused computer". You would need to put the entire plane with RX and ignition set-up on a scope to identify that problem via measurements.

Rob.m

the os max fx 46 ran with the home made carb. small success. at full throttle the jet needle was 0.2mm too small and the engine ran too lean full throttle. the only drill I had on hand was a 0.4mm. the nozzle was drilled to 0.4mm and this was much too rich idle mixture could not be adjusted well enough at -97 in the fuel curve was still too rich. After checking a standard 0.2mm print nozzle under a microscope I saw that there was a burr in front of the hole. which was drilled only 0.25mm and further processed into a nozzle needle. Will test again soon to see if it runs better.

cmulder

On a glow rc carb the moving part/ barrel is in line/ around the spraybar.
This is to be able to change mixture between full and idle by moving the barrel away from the spraybar or closer.

The solenoid system makes all of that redundant.
So is there still a need to have the spraybar and air valve combined?
Would a seperated system like this cox air intake limiter before the needle also work?

cox trottle

1967brutus

Probably it would work, but I think there will be issues with the greatly varying vacuum when for example coming off the throttle or accelerating. For constant RPM/variable load situations like for example a helicopter with governed RPM, this might work pretty well, and it is something I am going to consider when rebuilding the .50 gasser heli that I crashed a while back...

1967brutus

Posting this for Rob.M, because he does not yet have the possibility to link pics or vids:

https://uploads.tapatalk-cdn.com/202...4f54e02515.jpg

https://uploads.tapatalk-cdn.com/202...1bdd0396a6.jpg
If the links won't work, I'll figure something out...


This is yet without airbleed. Rob has flown it, and reports excellent behaviour in the air, and good adjustability of the fuel curve, BUT, same like Chris, a slight irregular idle, so his next step will be a tiny airbleed hole to see what happens.

Having given this a bit of thought, I think, that this irregular idle is caused by the pretty low fuel opening values of the curve: the solenoid is open for a very short amount of the total time, and due to its fixed frequency while the engine runs "whatever it likes to run" some valve openings are in the middle of the induction stroke, others are while the induction port is closed, and some induction strokes occur with fuel supply, others without, resulting in a varying mixture strength in the buffered mixture in the crankcase (at idle, it is my estimate that the total refreshment rate of the crankcase volume is less than once per 10 revolutions so when supply is intermittent, that leads to varying average mixture strength).
The use of either an LS needle OR an airbleed will force the fuel curve upwards, which causes the solenoid to be open for a larger percentage of time, reducing this effect.

Anyway, whenever Rob has time, I think I'll have a few 2-strokes that could do with a new carburettor

What is nice to see, is that also THIS idea, is repeatable by others, and for that, a big thumbs up to Chris, and just as big to Rob for proving that.

I love seeing these developments, and I an sentenced to spending a month on a ship in the gnawing knowledge that when I come home, there will be a plane at the clubfield that I am going to be "slightly jealous" of...

cmulder

There is nothing in those forum rules that the first 10 (?) post have to make sence.
Post about the weather or what desert you had for dinner.. No one here is going to complain

just a thought (and another post to inflate my stats