help please

[j taylor]

hi to anyone reading this post
i need help with a circuit that will start a generator automatically when my batteries reach a predetermined state of charge and stop the generator when the batteries are charged again can anyone help
many thanks
john

[Inquorate]

stop and start

Try two zener diodes, one with 12v breakdown voltage to switch a pnp transistor on, and a 15v reverse breakdown voltage to turn a npn transistor off when it's full.

Gyula knows these things best though.

[morpher44]

solar engine

This "solar engine" circuit is a nice little circuit
to run a motor or charge a battery or some other load
when a charge builds up to a certain point.

It is easy to replicate and might be useful in a little robotics application.

BEAM Circuits -- T3SE type 3 SE

[gyula]

hi to anyone reading this post
i need help with a circuit that will start a generator automatically when my batteries reach a predetermined state of charge and stop the generator when the batteries are charged again can anyone help
many thanks
john

Hello John,

I assume you mean 12V batteries, ok?

Perhaps the simplest is here: Printer Friendly Version

You have to use a hefty (high current automotive) relay of course with another independent (NO=normally off) contact pair beside those shown in the schematics and this extra contact pair should be wired to switch the generator on and off.
Of course you have to omit the 15V charger part of the schematics on the right side and replace it with your generator DC output (I mean the mains transformer, the diode bridge and the puffer capacitor) because I assume your generator circuit includes the bridge rectifier.
(Notice: in the schematics you can see typos, the letter V should be Ohm i.e. next to the VR1 500 Ohm, R2 290 Ohm and R3 15 Ohm.)

Here is another circuit, you have to combine a relay control transistor at one of the LED or buzzer outputs to switch on your generator, http://www.electronicsforu.com/EFYLi...-lead-acid.pdf

(Put a wire jumper to short circuit the push switch S2 for good. Also, use wire instead of the piezo buzzer.)

rgds, Gyula


PS @Inquorate: Thanks for your kind reference to me.

[j taylor]

Thanks guys will give printer friendly version a try i think

[gyula]

Thanks guys will give printer friendly version a try i think

Hi John,

I hope it is not too late to tell you that my suggestion of omitting the mains transformer and the diode bridge makes the whole circuit unoperable because this removes the voltage source for the relay as well. I have just realized this when giving a second thought to this circuit.

There is a simple solution: if you use the battery voltage via a series diode to supply the relay, then there is no need for the mains transformer or any other outside voltage source. (Of course your generator cannot be used for this purpose because it is just the relay that should start your generator but it cannot do so if it has no supply voltage to operate from...)

So all you have to do is to connect a diode (1N4001 is fine), its anode goes directly to your battery positive pole and its cathode goes directly to the NC (normally closed) contact of the relay, ok? This way the battery (instead of the mains supply via the diode bridge) will supply the positive voltage to the transistor collector and the relay whenever the rely should be switched either ON or OFF as the discharging - charging process dictates.

Sorry for this mistake, hope you understand the problem and the remedy.

rgds, Gyula

[j taylor]

just a little more help

HI Gyula
Thanks for the link to the printer friendly circuit and the other info in your posts and yes your last post was in plenty of time as i haven't got round to building the circuit yet i am in need of a little more help if that,s OK can you tell me what kind of transistor Q1 is and also what RL1 is many thanks
john