Need help finding a buffer!

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jpeezy

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Im trying to build a device that will deliver 0-5V to a matress air pump to a relay switch. One of my friends recommended that I need a buffer in the circuit but I don't know which one to pick. I'm at a complete loss since it is my first project involving electronics. Please help! I've attached some diagrams my friend drew up
 

Hi Jpeazy
Yes your friend is right . you should use a buffer . but not a buffer with op amp . as i understood you want trig a relay . hence a simple transistor would be ok . ( don't forget to use freewheeling diode )
Best Wishes
Goldsmith
 

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It's common to find mattress air pumps that run on 120VAC, or on 12VDC. Do you plan to run one of those on 5VDC? That will not be easy. You'll need a power converter of some kind.

Or do you have a pump that runs on 5VDC? And what is your power supply?

Your initial schematics show an op amp and motor. The rest is unclear.

It is likely you'll need to install a relay to turn on the motor. And (in agreement with Goldsmith) a transistor is sufficient to turn on the relay. A 50 cent op amp can turn on the transistor.

Is the op amp the center of your control circuit? Is it supposed to shut off the pump when the mattress reaches a certain pressure? Do you plan to sense air pressure directly? Or sense when the vinyl reaches a certain tension? Or sense when the pump starts drawing more amps?

I imagine the $4.82 (plus shipping costs, from Digi-key) op amp buffer can cover a couple of duties, however you might be able to get by with two components for less expense.
 


The plan is to use a foot pedal to deliver a voltage of 5V to the air pump which is either connected to the wall or that already has batteries inside of it. The buffer amp is only at the center to illustrate my friend's suggestion. there is no special meaning to it. I already have the DAC and

I was also curious about the other photo graph. It supposed to be below the amp in the middle. He though about the buffer amp because he wanted to prevent any current backflow from the pump.
 

Questions:

Have you made certain that your 5V power supply is able to operate the pump? (My guess is a few amps are involved.) If you are thinking of using batteries, four D cells may or may not be sufficient.

Does your 5V power supply have an existing switch, and you want to replace it with a relay?

If it does not have a switch, then does it have someplace to hook up a switch or relay?

If it does not have a place to install a switch, then you will need to do some work. You will need to clip a wire somewhere. Or else open up the housing (risky if house current wiring is exposed inside). Furthermore a typical power supply is liable to be tough to get apart.

By the way, if you absolutely need a foot switch, there is no more straightforward way to install one than the schematic below.

 

Thank you for your suggestions. I was able to pick out a few buffers. I'll post links if you want to take a look at them.

I think both have their own switches. One just runs on batteries and the other on wall power. I can't test the power supply until I build the circuit.

 

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