Question: Choosing/Using an SSR

Oct 06, 2007 4 Replies

I'm working on a circuit to replace a wired remote control unit with an RF remote. The existing remote is nothing more than 3 push buttons that connect a 5V supply voltage to ground via a 470 ohm resistor (remote connected via some RJ-11 connectors and a phone cord. The buttons are UP count, Down Count, and Reset.



I'm having some trouble interfacing the RF remote circuitry with the wired remote interface. My plan is to use 3 SSR's in place of the existing push button switches. The RF remote works great, and lights up test LED's just as I would expect when push buttons on the transmitter are pushed. My next step was to replace the LED's with the SSRs. I chose the SHARP PR22MA11NTZF to do the job. I connected pin 2 to ground, and 1 to my output. Then I hooked up pin 6 and 4 to my continuity tester and hit the buttons on my transmitter. Everything looked like it was going smoothly. The SSR was behaving just like the switch. When I held the buttons down, I got a solid buzz, when i hit them fast, i got short blips. Then I replaced the continuity tester with the wires I wanted to short (+5V from the circuit i am driving, and Gnd (via a 470 ohm resistor).



Here is where my problem was noticable. I push the button one time, it latches the SSR, causes the circuit to count as expected, but then never unlatches, so even after i release the button my circuit keeps counting. I'm assuming I have either chosen the wrong SSR, or need different circuitry somewhere as it behaves as if the current flowing through the SSR after the initial button press is holding the switch on, when I want it to turn off when the drive logic turns off.



Any ideas? If someone could point me in the right direction for a more appropriate SSR, or SSR circuitry that would be great. Thank you in advance for any assistance you can provide.



chris snipped-for-privacy@hotmail.com wrote: (snip)

This relay is intended for AC loads. Its output device is a latching thyristor that relies on the current zero crossing twice per AC cycle to reset it to a nonconducting state.

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Your test meter does not draw enough current for the thyristor to latch on, but your intended load does.

You need an SSR intended for DC loads (mosfet output or photo transistor) If your load current is a few milliamperes, you may get by with an ordinary opto isolator like one of these:

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If, instead of just describing your circuit verbally, you could also post a schematic somewhere, (alt.binaries,schematics.electronic would work) then we wouldn\'t have to guess about what "solid buzz" and "my circuit keeps counting" means.

Oops... alt.binaries.schematics.electronic

That's how they work. once current is moving through the SSR's, they stay latched until the current drops below the holding point. if you're dealing with DC volts, use logic type fets.

"I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5

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