Voltage amplification

gez · March 14, 2009, 01:33:35 PM

Why aren't you just using transistor drivers for your relays?

gtrplaya101 · March 14, 2009, 01:33:45 PM

Could I do something like the following:
http://www.wisc-online.com/objects/index_tj.asp?objID=SSE3703
I don't see why this wouldn't work

gez · March 14, 2009, 01:35:29 PM

Quote from: gtrplaya101 on March 14, 2009, 01:33:45 PM
Could I do something like the following:
http://www.wisc-online.com/objects/index_tj.asp?objID=SSE3703
I don't see why this wouldn't work

The collector resistor will be in series with the relay input. It will drop voltage.

gtrplaya101 · March 14, 2009, 01:41:31 PM

crap... yeah your right. So i guess I'm back to what an op-amp? The reason I'm not using a transistor to control the relay is cause I couldn't get it to work. I cant really turn back and redo it now since Im basically done with the project. Everything works except the activation voltage. Im looking for something I can graph into the existing circuit. I can show you the layout I used if it will help at all.; Maybe you could figure out if a transistor replacement would work. Thanks

gtrplaya101 · March 14, 2009, 01:45:14 PM

OK nevermind I know I cant graph a transistor into my circuit. So back to very original question how do I get 2v to 6v? Op-amp? Gain of 3?

gtrplaya101 · March 14, 2009, 02:04:43 PM

Would this work, its a tlc271

kvb · March 14, 2009, 02:31:16 PM

you need to have a "summing amplifier".

The summing amp would be running at ~9v. If it is bipolar power, I think you need a LM324
one of the voltages at the input of the SA would be 2v; output =2v
then when you connect 4v at the SA the output would be 6v

A summing amplifier looks like an inverting amp with more than one input resistor.
look up op amp tutorials

Gus · March 14, 2009, 02:33:06 PM

page 4
http://www.datasheetcatalog.org/datasheet2/3/06r40sd9fz70fpzo8qrypz2k91fy.pdf

Note the current drive of the chip it is under 12ma at 5v. What is the current needed at 5VDC for the coil of the relay? 5VDC/coil resistance = the current

What you need is a transistor buffer with the relay coil as the collector load make sure to use a flyback diode across the relay coil

Google things like TTL output drive circuits,TTL interfaces, TTL buffers, TTL relay drive circuits etc.

Always look up the drive current of the devices output, in this case the mm74c373

gtrplaya101 · March 14, 2009, 03:05:56 PM

Yep you are correct the relay requires 72 mA so the current would not be correct.
Here is the circuit i'm dealing with. Any way to mod this into something I could use with a transistor?

waky · March 14, 2009, 10:45:05 PM

ok, so now i wonder =/... Why wouldnt a simple schmitt trigger work to control the relay ?

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Voltage amplification