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DennyMo
06-10-2010, 11:01 AM
I'd like to build a simple controller for 2 channels that will power channel A for 5 minutes, then switch to channel B for 5 minutes, back and forth until powered down. I found a circuit using a 555 timer:

http://www.kpsec.freeuk.com/images/555diode.gif

Could I have both relay circuits driven off of the same output of the 555? Or should I used a separate 555 output for each channel? Or do you have any less expensive/easier suggestions? Thanks.

blickensderfer
06-10-2010, 11:17 AM
Denny,

You could use this led flasher circuit and replace the leds with your optocouplers and attach your TRIAC and you would have an alternating SSR circuit.

http://www.josepino.com/light/led-flasher-circuits1

dnesci
06-10-2010, 11:56 AM
The circuit in your diagram is in simple form. You would have to find relays that would consume a low current. Most diagrams similar to the one you are showing use NPN and PNP transistors to drive the relays.

But to answer you question, you could make it work.

Don

DennyMo
06-12-2010, 12:38 AM
Thanks for the replies. Looks like that modified LED flasher circuit would be a better choice.

DennyMo
08-04-2010, 10:23 AM
Further Googling found this kit:
http://www.canakit.com/60-minute-1-hour-adjustable-on-off-cyclic-timer-kit-ck191m60-uk191m60.html

Am I correct in my understanding that if circuit A is connected to the NO side of the relay, and circuit B is connected to the NC side of the relay, it will accomplish what I've described above? Thanks.

Mactayl
08-04-2010, 11:22 AM
You could use the dual 556 and set up the rc values so that when one of the timers time out it would trigger the next for less then 10 bucks but it seems that you may already have something you can get pre made.
good luck

DennyMo
08-11-2010, 11:01 AM
I had almost convinced myself to go with the Cana-Kit, but changed my mind when I priced out the components to DIY and factored in "the joy of learning".

You could use this led flasher circuit and replace the leds with your optocouplers and attach your TRIAC and you would have an alternating SSR circuit.
I chose a different LED flasher circuit to use as a starting point:
http://www.kpsec.freeuk.com/images/555leds.gif

- If I go with the 859-MOC3023 opto (like on the SSRez), I need to get the voltage on pin 1 down to 1.5V, right? Is that a standard voltage for all optocouplers?

- Using the 555, does it really matter whether I go with Vs of 9VDC or 12VDC? Any compelling reasons to choose one over the other? (Obviously, it affects the pull-down resistors on the LED/opto.)

- Are the resistors shown in the correct "order", relative to the LED? Shouldn't they both be on the same side of the LED (or opto, in my case), or does it not matter?

Thanks.

somtng4u2c
08-11-2010, 11:29 AM
Further Googling found this kit:
http://www.canakit.com/60-minute-1-hour-adjustable-on-off-cyclic-timer-kit-ck191m60-uk191m60.html

Am I correct in my understanding that if circuit A is connected to the NO side of the relay, and circuit B is connected to the NC side of the relay, it will accomplish what I've described above? Thanks.
Don,t know why not.

dmcole
08-11-2010, 01:29 PM
- If I go with the 859-MOC3023 opto (like on the SSRez), I need to get the voltage on pin 1 down to 1.5V, right? Is that a standard voltage for all optocouplers?

Yes, I believe so.

- Using the 555, does it really matter whether I go with Vs of 9VDC or 12VDC? Any compelling reasons to choose one over the other? (Obviously, it affects the pull-down resistors on the LED/opto.)

Well, it will also influence the capacitor/resistor combo that drives the 555. Remember, all a 555 does is "flips a switch" when the capacitor completely drains out.


- Are the resistors shown in the correct "order", relative to the LED? Shouldn't they both be on the same side of the LED (or opto, in my case), or does it not matter?

Doesn't matter. It's resistive within the total circuit.

FWIW, I fooled around with 555s a lot a couple of years back, trying to build a railroad crossing flasher (you know -- left/right, left/right, over and over) -- I never actually got the circuit to work because I couldn't get the resistor/capacitor combo for the 555 for the speed I wanted. I finally ended up using a PICAXE microprocessor, which uses a light-weight BASIC-like programming language. Obviously overkill, but once I switched to that chip, I had my crossing flasher working within a day or two.

YMMV.

\dmc

sjwilson122
08-11-2010, 02:52 PM
555 timers are actually easy to use and should work well for what you are trying to do. Here is a link with lots of good info on them and even a calculator so you can figure out the flash rate.

http://www.bowdenshobbycircuits.info/555.htm

DennyMo
08-13-2010, 09:57 PM
Thanks for all your comments and suggestions. I've finished two schematics, one with a 555 the other using the 2-transistor flip-flop. By my calculations, both versions give me ~5:30 in each state. I could play with the RC values a bit and get it more nearly to 5 minutes, but the standard component values get me close enough (and are cheaper and easier to install).

I've borrowed from the SSRez design, and consulted http://www.kpsec.freeuk.com/index.htm heavily. (Hit Bowden's site a lot to, it's been in my favorites for a while.)

If any of you see any problems here, or have any suggestions or "why'd he do that" questions, please let me know. I have a couple questions of my own:
- 5A fuse on a 4A triac, I think I got that backwards, should the fuse be smaller?
- What voltage for the caps? I've seen online suggestions that 16V or 25V is OK, is that correct?