Verification of Charging Circuit

by Mastermime on Tue Feb 12, 2013 6:51 pm

Hello I was wondering if one of you could just verify my charging circuit (left part of circuit). I'm trying to charge to 7.2v nimh batteries with one charger.

Thanks
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Re: Verification of Charging Circuit

by Zener on Tue Feb 12, 2013 7:54 pm

What happens when you close the toggle switch? Looks like... kaboom...
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Re: Verification of Charging Circuit

by Mastermime on Tue Feb 12, 2013 8:47 pm

Whoops. how did I not see that... I could just add a transistor inbetween one of the positive lines from charger there right? When a 7.2v is connected, a signal will be sent to the gate, connecting collector and emitter, right? Would I need this on the ground line as well?

Note: I forgot to mention, but I am using xlr connectors for charging
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Re: Verification of Charging Circuit

by Zener on Tue Feb 12, 2013 8:57 pm

That still looks suspect. Please explain what you want the switch to do. Why do you need a switch? As far as XLR's for power, I never heard of doing that. I guess you could.
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Re: Verification of Charging Circuit

by Mastermime on Tue Feb 12, 2013 9:28 pm

Well the mechanical switch is for turning the circuit on or off when the charger is not plugged in. The transistor will break the parallel connection between the positives of the two batteries, but when the charger is plugged into the xlr port, 7.2v will flow to the gate of the transistor bridging the connection.
The transistors are just for charging.

The reason I need to do this because I cannot find a cheap 14.4v Nimh charger. If I had this I could just charge the batteries in series. I already have a 7.2v charger so I can charge the batteries in parallel

Sorry I should have incorporated the xlr connectors in the schematic.
Also I believe I need a transistor on ground too

I hope this answered your question
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Re: Verification of Charging Circuit

by Zener on Wed Feb 13, 2013 8:28 pm

So that transistor is like a "trans-diode"? I am unfamiliar with that. Can you explain how that will work?
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Re: Verification of Charging Circuit

by Mastermime on Wed Feb 13, 2013 8:48 pm

I'm not sure what your talking about when you say transdiode. Isn't it basic electronics or am I missing something?

No 7.2v and toggle on: +s arent connected, grounds aren't connected, batteries operate in series


7.2v toggle off: Activates transistor connection when current goes to gate, +s and gnds are connected, series connection broken (toggle off), parallel battery charging connection
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Re: Verification of Charging Circuit

by Zener on Wed Feb 13, 2013 10:01 pm

I have never seen the base connected to the collector like that. Did you see that some where? Why would they have 3 legs on the transistor if you are only going to have 2 connections?
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Re: Verification of Charging Circuit

by Zener on Wed Feb 13, 2013 10:09 pm

That aint flyin' ...

I would use a 2 position multipole switch. Maybe 4 poles? Hook it up so one way it makes you charging connections and the other way it makes the running connections. Make sure it is fool proof.

Maybe someone else has a better idea.
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Re: Verification of Charging Circuit

by Mastermime on Thu Feb 14, 2013 4:51 pm

Wait a minute. Why wouldn't this work? Where's the flaw in my logic?
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Re: Verification of Charging Circuit

by Zener on Thu Feb 14, 2013 5:13 pm

Do you know how transistors work?
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Re: Verification of Charging Circuit

by Mastermime on Thu Feb 14, 2013 5:28 pm

Yeah when a connection is sent to gate a connection is made between collector and emitter. Electrons flow into collector and out the emitter
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Re: Verification of Charging Circuit

by Zener on Thu Feb 14, 2013 9:56 pm

That's a bipolar type you have there so no gate. That is a base. In either case it is very unusual to hook the base or gate to the collector or drain. I have never seen it. So I cannot recommend it unless you can show me why this is a great idea. It seems to me you are using it like a diode. In either case if you close the switch you will have a short through that "transdiode". I see smoke in your future. I would design it using a switch. Then once you have done that you can see if it can be fancied up. If this was easy everyone would be doing it.
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Re: Verification of Charging Circuit

by Mastermime on Thu Feb 14, 2013 10:23 pm

Whoops I'm so used to using MOSFETs, I'm getting my terms mixed up. The transistor is acting as an electrical switch! When charger plugged in, a connection is made, allowing me to charge in parallel, but when no current is sent to the base, the parallel connection is broken and I will be able to turn on the mechanical switch without. The transistors are there to eliminate the use of any unnecessary mechanical switched. I will test on a breadboard (first with a multimeter) and let you know my results.
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Re: Verification of Charging Circuit

by Zener on Fri Feb 15, 2013 12:18 pm

Yes a transistor is a switch but you don't have it hooked up that way. Where is Mstone when we need him? I don't know what transistors you are using so I don't know if they will pop or just get incredibly hot. In any case don't have your face too close when you throw the switch.
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