LED signal to open 7VDC CKT?

[motleypixel]

So what could be used instead? Just curious? I've been watching youtube videos on refreshing my memory on this stuff...ran across this DIY SSR...I'm curious as to the pros/cons of a coil relay like the one I'm going to use vs. a SSR? https://electroschematics.com/wp-content/uploads/2010/12/diy-solid-state-relay.gif

 

[Reloadron]

I like the cct, but dont understand why an opto isolater is needed??

The opto coupler was just one of several ways to go about taking an available signal and getting it to do what we wanted. A transistor could have likely been used. The use of an opto coupler as to isolation was not needed (for isolation). It was just a simple means to drive a relay.

Ron

 

[motleypixel]

Parts on order, had to get the 22ohm resistors at Frys. Did up a wiring diagram, now just need a breadboard to test or I may learn how to dress that copper clad board and make my own runs etc.

Okay I'm back...wow...crazy how life steers you in all directions. So this attached image is how I wired it and I almost damaged some components. Take of look of my hard-wire diagram above the schematic diagram you made. See the common line at the very bottom? I don't know why I did this when I made the copper clad board runs but essentially I made pin 4 of the relay common as well. When I connected it there was a short and high current situation and it actually burned off a small run off the common run of the copper clad. So now, can you just once over the hard-wire diagram I made in this quote and see if it all makes sense? If so, then I can open the run that makes the pin 4 of the relay common and give that a try.

Thanks,
Roy

 

[dougy83]

I just saw the circuit diagram above, and it's likely that the 4n25 is not able to drive a relay.. It's CTR (current transfer ratio) is only guaranteed to be 20%. you may want to put another transistor (with a resistor between its base and emitter to stop it turning on when it shouldn't) on the output of the opto.

 

[motleypixel]

Thanks for the help. Would this CKT work then? The only quandary now is the pin-out on the relay. I know pin 1 is the + output of the speed controller and pin 4 is the + side of the motor, but how do I connect pins 2 and 5? Pin 3 will be left open for when the coil in the relay is energized (cutting out the voltage drop across the motor).