Drive relay with opamp!

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#1
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I made this circuit,
It is not work true!
what is my mistake ? and how can I solve it?

I think the out put of opamp have resistor!
what is reason?

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Thinking Low-Level, Writing High-Level. http://art-net.ir

https://pejeshgi.com/

http://alinezarati.com

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What is the resistance of your relay? Most OP amps have some sort of current limiting in the output stage, which may make directly driving a relay impractical. Adding a transistor would be a better arrangement.

Tom Pappano
Tulsa, Oklahoma

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Might think about adding a positve feedback resistor for hysteresis. Use emitter follower as an output buffer.

It all starts with a mental vision.

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If you look at the specifications of the LM324 Op Amp, you'll find that it's not guaranteed to be able to supply more than 20mA of current when connected the way you have it. If your relay needs more current than this, it's overloading the output of the Op-Amp, and so preventing the voltage getting high enough to operate the relay. To be able to help further, we'd need to know more details about the relay you are using. You relay needs to have an operating voltage of about 12 volts, with a coil resistance of 600 ohms or higher for that circuit to work. (The 600 ohms comes from 12V/20mA)If the relay needs more current, or a higher operating voltage, then you will have to design some sort of buffer circuit in there to handle the higher power.

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ok thx for all,
my exact problem is I made this board, i can not really have big change in it,only add some redistor in it :D relays can't work with this amper.

now what your opinion?

Thinking Low-Level, Writing High-Level. http://art-net.ir

https://pejeshgi.com/

http://alinezarati.com

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If you can't change your board, then you have what is commonly called a "problem", and/or you are "screwed".

Tom Pappano
Tulsa, Oklahoma

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If you add a 1K resistor between pin 4 and 7 of the opamp you will get a 12ma boost in the output. The down side is the opamp will always be sinking 12ma at idle.

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tpappano wrote:
If you can't change your board, then you have what is commonly called a "problem", and/or you are "screwed".
:lol: :lol: :lol:

On a much less hilarious note, you may be able to simply replace the op-amp with a transistor in the same package, keeping your original PCB. Just get one that can source a couple-100 mA and saturates when Vgs/Vbe is about 5V, and be sure to limit its current. For a FET, gate goes to E1, (small resistor and) ground to source, resistor and high side of relay to drain. (See common source amp.) Watch out for signal current limits if using BJT.

If you can't find a transistor in the same package as the op-amp and with a pin-out that works, or if the CS amp doesn't provide enough current (need emitter follower/CC amp), refer to tpappano.

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You have not specified the cold resistance/operate current! It is difficult to come up with a design if we don't have all the facts.

It is foolish to make PCB's when you have not verified circuit operation. (Don't tell us thatyou have ordered a 1000 boards.)

To overcome the "big problem", just pretend that either your arse or your job depends on it. You can easily wire a ugly style transistor driver on your board. You can drill some extra holes on the board & use instant glue to hold the components in place and use the pigtails for interconnects.

If you can't do it the way it should be done, then do it the way it can be done!

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

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The LM324 has pretty standard pinouts for a quad op amp, you should be able to find an op amp with the exact same pinouts that has much greater drive capability.

You will just have to swap the opamp, if you are using through hole then it will be a bitch to desolder the chip, SMD would be a cakewalk with a hot air gun.

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If you use a TCA0372, that booger will hump out an amp.

Imagecraft compiler user

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I'm thinking run some leads off-board to an Amplidyne 8-)

Tom Pappano
Tulsa, Oklahoma

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What is the minimum current and voltage required for relay to operate (relay Detail??)

Check TLC2274

P.Ashok Kumar

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Never really liked those cross field amplifiers

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OK, thx for all reason.

and I tested some operation on it(not it->them it only 1 not 1000 board dear LDEVRIES) at the end I really decided to add transistor,
(It really difficult for me because board is metalyse)
relay are really powerful(16A with big package), using bc327 transistor can't run them and now I get lm324 out of board and put pin header instead it, using an other board connected to pin header that have TIP127 transistor for drive relay,

thx for all again.

Thinking Low-Level, Writing High-Level. http://art-net.ir

https://pejeshgi.com/

http://alinezarati.com