Harris
Senior Heliman
Location: A Greek in Cyprus
| Sorry guys, I didn't want to upset you!  I considered using the UBEC after reading all the positive comments about it. My .30 heli draws on average 450mA current, so the UBEC should work well. However, I hesitated because of its specs. I used the Duralite Batteries regulators for more than a year with no major issues apart from the odd kick of the tail. I then switched to the Fromeco ones simply because their specs are far superior from anything else currently in the market. When somebody else comes up with a better product I will probably switch to them! 
I think that within reason everything we do works, the difference is in the details.
Regarding the dual voltage option of the Fromeco regulators, they were meant to power your servos and receiver at a higher voltage, while still providing 5V to the gyro and rudder servo.
A few weeks ago I tried to connect an on-board glow system (Glow-2 from Ripmax) so that I didn't have to plug in my glow starter every time I needed to start the engine. This particular system needs 3-8V supply to the glow plug, which it then regulates automatically. I powered it from the receiver voltage to avoid adding an extra 5V battery pack. It would draw about 2 Amps whenever I needed to ignite the glow plug. During that time it caused quite a bit of interference and reduction of the antenna-down range of my Futaba PPM receiver. I also tried it with a Futaba PCM receiver and it worked without a glitch, but I decided not to use it just in case...
Initially I thought that the glow was drawing too much current and was dropping the voltage at the receiver end. However, I measured it and it was 5.1 V, i.e. exactly the same with the glow off. I then checked it with an oscilloscope and discovered that it was using pulse-width modulation to control the current to the glow plug. There were lots of very short spikes during the glow-on period. As soon as the glow was switched off the spikes would disappear.
This situation is very similar to the one you are talking about. I think you are going to see an awful lot of glitching simply because of the spikes of current drawn by the ignition system. Add to that the fact that you are introducing a direct link between your receiver circuitry and a 20kV spark generator (your ignition system) and you are in for an interesting time
You can try it if you want and post your results here but please be very-very careful! Do your range checks without blades with the engine both off and on, much like an electric heli. In theory it is not going to work, but who knows what's going to happen in reality! 
Harris |
