Voltate Regulator For EP Heli

[Hennisdk]

I bougth a Colco Thunderbird about 3 Months ago, and havent had a days trouble with it.

Now I want to use 3cell Lipo's in it, the only problem is that the voltage of the Lipo is to High 11.1V and the origanal pack is only 9.6V. The voltage difference in the Lipo fries the Main and Tail motor.

So what I am looking for is to build or get a SMALL voltage regulater that can handle at least 10 Amps and able to bring the voltage down to about 10V.

Thanks inadvance :)

Regards

DeathBunny

[rjet]

I don't know of any 10 amp voltage regulators that would fit on a heli, but 1 volt is so little that your speed control may be enough to be keep the motors safe, or just adding a couple feet of 26 gauge wire in series to the motors would likely drop a volt under full current.

[Miami Mike]

I agree, you wouldn't think that small voltage reduction would be enough to make the difference between normal performance and frying the motors.

Just the same, another way to drop the voltage would be to insert one or more silicon rectifier diodes in the positive lead between the battery pack and ESC. Each diode will theoretically drop 0.7 volts, but it would be best to check the result under power with a meter. Of course you'd use diodes with an adequate current rating. Voltage rating won't matter.

[Hennisdk]

The thing is when I have the Lipo fully charged the helicopter goes wild, the tail motor over works it self aswell as the main motor, and then they burn out.

When I only charge the Lipo to about 10V the Heli flies normal. But then it only flies for about 3 Minutes.

So the voltage does affect this heli quite alot.

Regards

DeathBunny

[jeffs555]

Have you tried looking in the micro-helis forum. http://www.rcgroups.com/forums/forumdisplay.php?s=&forumid=42
A couple of diodes in series with the tail motor might help.

[Miami Mike]

That's interesting. Apparently it's the speed controller circuits for your motors that can't handle the extra voltage.

As long as there's no damage now, my diode idea ought to fix it. The length of wire that Rjet suggested will only drop the voltage while current is flowing, and the drop will be in proportion to the current. Diodes will give you more of a fixed voltage reduction, but don't put them in series with the motors. That won't help you. Instead, just like I wrote above, wire one or more of them in a single row into the positive lead from the battery to the ESC, each with the stripe pointing toward the ESC.

[rjet]

Diodes should work well as long as they are used in series to the tail rotor or current is only a few amps or they can be paralleled, but I am concerned that in series to the main motor the heat dissipation may exceed one or two watts per diode (0.7 volt * amps = watts) and could blow up while flying.

[TMorita]

See this thread:

http://www.rcgroups.com/forums/showthread.php?t=99873

Toshi

[Miami Mike]

...I am concerned that in series to the main motor the heat dissipation may exceed one or two watts per diode (0.7 volt * amps = watts) and could blow up while flying.Like I said before, of course you'd use diodes with an adequate current rating. There's no need to work out any power formulas since diode current ratings are derived from them in the first place.

[Hennisdk]

Thanks MMike I think I am gonna try that Diode thing, can you suggest any model numbers for the diode's.

Thanks for all the feedback.

Regards

DeathBunny

[Comatose]

Like I said before, of course you'd use diodes with an adequate current rating. There's no need to work out any power formulas since diode current ratings are derived from them in the first place.


Given "ideal" heatsinking... In free air with no heatsink the current carrying abilities of large diodes is much less.

[Miami Mike]

There must be hundreds of different types that would work equally well. I don't know what sort of electronic parts suppliers you have in South Africa, but there ought to be a local store where you can simply walk in and ask for silicon rectifier diodes with whatever current rating you need. All that really matters here is the forward voltage drop and the current rating.

(And if you believe what Comatose wrote then get diodes with a higher current rating than what you need. It won't really matter.)

[Hennisdk]

Thanks, you guys have been a great help!!

Here in South Africa, if you walk into a store and ask for silicon rectifier diodes they will look at you in disbelieve :confused: . Last weet I was looking for a LM383K Variable regulater and they told me that you dont get an type of LM regulater :eek:

Regards

DeathBunny

[Comatose]

At 7 to 10 watts, its not going to matter if its a 25A rectifier diode if you don't heatsink it. It'll melt just as fast as a 10A diode in the same package.

A to-220 package has a thermal resistance of around 60 degrees C per watt. Without a heatsink, at 10A and .7v, the diode will be a comfortable 420 degrees C.

Linked is a datasheet for a 15A, to-220 rectifier diode. If you were to put this or any other 10A diode with a .7v drop in series with your motor without a heatsink, the following will happen. You'll take off, and within a minute or so the diode will either die internally or the solder holding it on will melt and fall off. Either way, you'll have no power and no control.

If you put the diode completely outside the body of the helicopter so that its in the main rotorwash, that might provide enough thermal dissipation that you could get away with it, given a sufficiently large package (to-247 might work.)

Again, I'm provinding this datasheet as a counterexample, not as a recommendation. This is a 15A diode, but it will NOT WORK in this application without a heatsink. You'll need a heatsink that at maximum has a thermal resistance of 10 degrees C per watt.

http://www.fairchildsemi.com/ds/IS/ISL9R1560P2.pdf

[OmegaDot]

You could increase you gear reduction by 9.6/11.1 (or close to that). Or, trim your blades a bit. Why would you want to waste your "precious" energy as heat in a diode?

[Miami Mike]

If it was that simple he could simply pull his throttle stick back a little and everything would be okay, but judging from his description, the problem seems to be caused by too much voltage going into his ESC:The thing is when I have the Lipo fully charged the helicopter goes wild, the tail motor over works itself as well as the main motor, and then they burn out.If that's correct then adjusting gears, trimming blades, or adding diodes in series with the motors won't help. He needs exactly what he asked for in his initial post, and diodes in series with the battery leads ought to do the trick.