Another good model augered in.

Well I've been wondering about starting this thread for some time. It seems that BECs', that's battery eliminator circuits, are becoming more and more unreliable. Hardly a week goes by without you read about someones model going in at speed with no control. I don't like BECs', I use them, but I don't like them, if you get my drift. To me, zapping a 5 or 6volt appliance with the full battery voltage for tiny amounts of time, to make an average of 5 or 6 volts seems cruel and ultimately destined for failure. I'm talking about switching BECs of course, linear ones are fine by me. The problem still exists though, if your ESC (electronic speed controller) goes down, your model is sure to follow.
Better to cut the Red wire that goes between the ESC and the receiver and give the receiver its own power.

Think about it, a 2900mAh 4 cell Nimh pack weighs 125gm and gives 4.8volts, if you need a bit of extra servo speed and response, try a 5 cell pack for size, weighs in at 155gm. On a 2kilo model it's only 8% extra. Is it really going to make that much difference? Just look at the benefit, if you fry your ESC, or your main Lipo goes belly up, you still have control, you just have to 'dead stick', the IC guys have been doing it for years! Perhaps someone with figures at their finger tips can give us an indicator as to how long 2900mAh will last, quite long is my guess, not so long ago we would fly all our flights on 600mAh. Of course we didn't have digital servos in those days (I still don't)

I'm going somewhere here Phil, give me time, I've got to warm up the brain cells.

Ok, so 125grams is not acceptable, how about less than 10? And you can choose 5 or 6volts! What you need is one of these

And it only weighs 6.7grams!

The PC board is only 22 x 38mm and you can go as high as 30volts input voltage. Without a heat sink the 317 will happily give you 1amp in still air and 2amps with a simple heat sink made of a thin piece of cake plate. Remember for you application you've got a big fan at the front to take care of airflow.
It's not all plus however, the 317 takes 1.2 volts for itself, so if you're using 2S then you'll have to settle for 4.8volts at the Receiver!
Not enough say you, I want more amps! Help is at hand, you can change the LM317 for an LM338. The 338 will happily give you 5amps all day!
One of these babies and a fuse and the only time you'll ever lose a model is if the Lipo has a catastrophic failure!
More tomorrow, plus instructions.

You'll need these.

Well, time to wrap this up.

We need the regulator, obviously! Two Lucar connectors, the blue ones, the red ones are too small, and an automotive fuse. It's the green one on the right, 30amps, the motor manufacturers have been using them for years. If you need more than 30amps you'll have to go for the yellow style of fuse on the left, also available from any good motor spares shop.
You can see I've already removed the red wire from the ESC and insulated it. I've also cut the blue insulation off the connectors, this is because we're going to solder them on. The commonest cause of failure in electrical faults is badly crimped connectors that overheat!
I checked my Funcub the other day, it's got 6 servos, my clamp meter on peak hold showed 1.5amps waggling everything.

You'll note that I've given the regulator a heat sink, cut from the light weight foil you get on the top of a coffee tin.

I've cut the red lead to the ESC and soldered a Lucar on the two tails, a nice bit of heatshrink and plug the Lucars onto the fuse.
Next solder the input leads for the regulator onto the ESC side Deans connector, and heatshrink.
At this stage I plugged in a battery and set the output voltage to 6volts. Connect a plug for the receiver and connect up!

All hooked up with an Orange receiver

Lovely!

I'd have put a small metal washer between the foil and the nut, to act as a load spreader, and also increase the transfer area for the heat.
I note also that you have not fitted an anti-parasite oscillation cap across the input and outputs of the regulator. On the LM series, they are recommended.

3mm washers are like rocking horse manure in my den! But you're right, as as for the capacitors, I haven't got enough brain cells, I just used the kit as supplied, do you mean a little capacitor in parallel with the electrolitics on the input and output?
By the way, total overhead including wires, 12.5grams!

Usually 1 micro across the pos and neg on the input, and 1 micro across the output and neg, stops the ic in the LM from oscillating itself into thermal runaway. Usually they aren't really needed, but if you get a funny load on the o/p, it can de-stabilize the circuit.

Also - for the experimenters, if you put an r on the common pin of the ic and THEN take it to 0 volts through the r, you can vary the output volts upwards, as shown on the circuit diagram.