Solid state relay replacement

Hi,

I'm currently using a photovoltaic solid state relay (Fairchild HSR312L) to open or close the path of a square wave signal. It works fine but at over a 1$ per unit it's rather hard on my circuit budget. I tried to replicate the internal circuitry of the chip (see datasheet:

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by using two MOSFETs with their sources connected together but I can't seem to turn off the switch (open the path). Anyhow, would anyone have a suggestion of a low cost, low current consuming solution to replace the HSR312L?

Thanks!

Reply to
Signumx
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I forgot to mention that the isolation is not required. Here is a summary of my project. We buy a unit that controls DC motor. Right now we also buy an off-shelf wired remote control which has simple SPST switches to open or close what seems to be current loops (I measure

40mA when a loop is closed). We want to add a module between the remote and the control unit to allow or prevent some of the remote keys to function. This needs to be managed electronically (or digitally). A 0-5V signal would take care this. Also, I've been told that the the return path of the control signals is not connected to the unit's GND. Therefore, I can't put my module to the same ground reference as the unit.

In brief, a HI signal would allow the loop to close and current to flow and a LOW signal would open (or put in high impedance) the loop.

Thanks.

Reply to
Signumx

It is exceedingly rare that you can build something with discrete components for less money than a large-scale manufacturer has already built as an integrated circuit.

-Robert Scott Ypsilanti, Michigan

Reply to
Robert Scott

I don''t think you'll get isolation for less than $1 each. If the isolation requirement was removed, it might be possible but still kinda tight.

Maybe if you shared more about what the circuit is attempting to do we could be of more help.

Reply to
Mook Johnson

If you need to get a singal that is referenced to one ground to appear on another non-connected ground, you need isolation.

I think you're at about as cheap as you can get for this part.

Reply to
Mook Johnson

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