Auxiliary drive

[Andy StonemanParticipant @andystoneman15177]

Ive made an Auxiliary drive unit but am having trouble with the battery getting hot when in use, I have tried different wiring combinations but the batterys are still getting hot, Could anyone put me straight please.

[Andy StonemanParticipant @andystoneman15177]

[Keith LongParticipant @keithlong89920]

Andy

We're going to need more information than that to help. A wiring diagram, details of the batteries, wiring and what is being powered for a start. More detailed pictures would help as well.

Keith

[Dave MilbournParticipant @davemilbourn48782]

The switch appears to be shorting out the battery terminals when switched on, although it would be clearer from a diagram. Also those PP3 wires are marginal in current-carrying capacity for a motor.

Dave M

[Andy StonemanParticipant @andystoneman15177]

Dave,

The wires and motor dont get hot just the battery, Dave, What your suggesting might well be right which is making the battery hot.It makes no difference if the battery is either 2×1.5v or a 9v they both still get hot.

Andy

[Andy StonemanParticipant @andystoneman15177]

Faulty wiring diagram, I have tried to alter the wiring but it only bypasses the micro switch and drives the motor directly, Still very confused.

Andy

[Dave MilbournParticipant @davemilbourn48782]

Andy

(The photo seems to differ from the diagram so I'll stick to the latter. BTW neither will work!)

The switch in your diagram is redundant in that the two terminals you have used (NO and NC) will never contact each other. If they were to do so then there would be a direct short-circuit across the battery – which would blow up. You have the battery permanently connected to the motor, which will continue to run as long as the battery remains connected or until it goes flat. Please have a look at my article in the most recent Model Boats Winter Special about electrics – this explains switches and circuits. Also it's not a good idea to run a motor rated at 3v on a 9v supply. Both the battery and motor will get hot until the motor burns out.
Your wiring should be:
1. Battery positive to switch 'COM' (Common) terminal;
2. Switch 'NO' (Normally Open) terminal to one motor terminal;
3. The other motor terminal to battery negative.

Finally you should be using a plastic propeller with 3 blades and of 25-30mm diameter only. Anything larger will overload that (very fast) motor.

Dave M

Edited By Dave Milbourn on 13/01/2014 08:48:49

[Malcolm FraryParticipant @malcolmfrary95515]

If the battery is getting hot, it is being overworked. This can be because the motor is demanding too much current, or because a wiring error has put a short on it. A shorted battery will certainly get hot, whether it gets hot enough to rupture is another question, 1st question is "what kind of battery?". If its a PP3, (guess, that being the commonest 9 volt battery using that kind of connector) it probably won't have enough power to harm its surroundings, but equally, it won't have the guts to drive a motor, either.

Find a battery of the same voltage as the motor rating, use that. 2 of AA probably the best bet.

Take the wires that you show going from the battery -ve away from the switch altogether.

Take ONE of the microswitch + wires and connect it to the terminal currently shown unused.

Looking back at the picture, the switch IS shorting the battery when the contacts make. This ensures that 1- the battery gets hot 2- there is probably going to be no power left for the motor when it is wanted. 3- that motor probably wants more current than the battery can supply. This means that much of the energy in the battery will go into heating the battery.

[Andy StonemanParticipant @andystoneman15177]

Thank you both for your help in resolving my wiring problem, I followed your instructions Dave and Malcolm and can report it works a treat, no more heating batteries. and the drive works as I wanted it too. Within reach of me there lives a Carpenter, Cabinet maker, Plumber, Doctor, accountant even a retired master Mariner, but no Electrician, Just what we need ! The reason I built it is in case I have any trouble with my steam set, Should that happen I can start the auxiliary which moves over and engages the flywheel of the steam engine. And should hopefully drive the model back ashore. Malcolm I would like to see your article on model electrics, Unfortunately we are still waiting for the winter issue to arrive here in Australia Apparently there is some delay where I live.

Andy

[Malcolm FraryParticipant @malcolmfrary95515]

It was Dave's article in the mag, well worth the read. He's the one with the looks and ability. I just get by on good luck.

[DanosParticipant @danos]

Hi Andy.

Just read the problem and glad you resolved it with the guidance of Dave and Malcolm. You can find all the publications on line and that's where I have subscribed. I get them on my computer, my iPad and even on my iPhone. I noticed that you live in Australia! I also live in Australia (Eltham, Victoria). Where about are you? Love to hear from you.

Cheers

Danos

[DanosParticipant @danos]

Hi Andy.

I forgot to mention, that if you ever need any urgent help feel free to call me. My number is 0414 290 230. I'll be happy to help. cheers

Danos

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