Voltage limitation

[Johnson]

Hi all,

I am currently building a car(how far away from building electronics can you get lol) which uses a motorbike engine.



I have had to fit an electric water pump due to the oil system I have to use so have purchased a digital controller the same as this

http://www.daviescraig.com.au/main/display.asp?pid=56

I need to reduce the voltage to the controller as it keeps going into test mode as the generator on the engine is producing up to 15.1 volts which is within the specs of the engine manufacturer.

I must admit I have not measured the amps yet but can do quite easily if needed.

How or what do I need to do to limit the voltage to the controller.I have limited electronics experience but have built a Megajolt ECU for my old car from a kit of parts so can solder etc but I dont know what I need to get/make to hopefully resolve this problem.

Many thanks

J

[Biffo]

A big chunky power transistor with a 12v zener diode on the base is basically what you need.

but for an easy life, adapt something like a lorry 24v to 12v power supply. Obviously check it works at 15 volts


something like this maybe
http://cgi.ebay.co.uk/12V-24V-120W-DC-D ... dZViewItem


alternatively, if your engine has a pulley or power take off point, just set it up with a bog standard car alternator , these are regulated to 12v.

[Johnson]

Thanks for the reply Biffo,

I like the sound of the first option any ideas on what parts I need exactly please?

J

[Biffo]

Here is a typical power supply circuit.

http://www.zen22142.zen.co.uk/Circuits/ ... 230psu.htm

this is for a mains input, but all you have to do is remove the transformer and bridge for your requirements

The regulator chip will give you a stable 12 volts all the time , the six large transistors
are there to handle the amps which in this case is 30A (I would assume the author has used this arrangement as the 2955's are comparitively very cheap and well known)

contact the author he would probably bespoke it for you