ORIGINAL: Big feet
Hi Guys,
I know a lot of time has passed since I first posted this problem, other projects took over.
Last week I made some more tests on the Evolution 35cc interference problem.
Test 1 Connected power directly into the Rx and Ingition unit. No difference.
test 2 moved the batteries, IGN battery temporially cables tied to the UC, and Rx battery as far rearward as possible. No difference.
Test 3 Tried another Rx, only connecting the thro and one elevator. No difference.
test 4 Tried a different plug (resistive type). No differnece.
The engine runs Ok for a very short time, up to 10 seconds, then stops suddenly. Not ceased, it stops firing and stops rotation normally. This happens from idle or even third throttle, running smooth until the sudden stop.
After all of this my guess is a faulty IGN unit, which is also causing the interference. Any other suggestions?
If this seems a fair diagonisis, which system is the best/easist retro fit. The Evolution system is $229, silly price.
The CH system and rcExl units are much cheeper and from what I've read on here, well respected units.
Any assistance appreciated,
Cheers,
Peter
Peter,
A couple of things: first, I tried running an FM radio on 72 MHz on a gasoline powered truck that has a 26cc magneto ignition engine. I had the same sysmptoms you described...radio worked great until I started the engine, then everything would go haywire. I changed the tx and rx to 2.4 and problem was solved. Nothing generates more RF noise than an old style magneto ignition, and the proximity of components in a RC truck makes radio requirements much more demanding than in an airplane. I seriously doubt the problem is in the radio
Your specific description brought to mind a recent event in my airplane set-up, also on 2.4 Gig. The engine is a 30cc gasoline engine with RcExcl CDI unit. I was running a separate batteries for ignition and radio. The ignition battery was a 2 cell Li-ion and the radio a typical NiMH. Everything would work great as long as the engine was down. Soon as I started the engine everything would go haywire.
I traced the problem to a faulty ignition battery. Even when "fully charged", this battery was old and had developed so much internal resistance that the CDI unit would drop voltage below a usable range for the CDI (around 4 volts).
Take another look at your batteries and use fresh on the ignition.
MattK