I'm looking for a way to do the following:
Once triggered, the circuit will
- close the first relay (R1) for 10 seconds, then open
- then close the second relay (R2) for 10 seconds, then open
- have a pause of 60 seconds until it can be retriggered.
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\$\begingroup\$ So can you design a circuit which will output two pulses with given timings? \$\endgroup\$– Eugene Sh.Commented Aug 11, 2015 at 14:19
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\$\begingroup\$ Use 556 chip for that. \$\endgroup\$– AlexxxCommented Aug 11, 2015 at 14:23
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1\$\begingroup\$ Use a microcontroller if there are no preferences. \$\endgroup\$– nvdCommented Aug 11, 2015 at 14:26
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1\$\begingroup\$ I agree with @nvd. A micro would be the most flexible. You could use ATTiny in the 8 pin DIP package. No external components (except for the decoupling cap) and lot more stable with temperature and aging. \$\endgroup\$– AlexxxCommented Aug 11, 2015 at 14:32
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\$\begingroup\$ With timer, use 555 with a decade counter with 10 outputs with reset. Set the pulse timing of 555 to 10s. At first output connect relay1, relay2 at the second output. Connect the 8th output to the reset of the counter. Somehow figure out how to wait for the next trigger while keeping 555 disabled in the reset state. \$\endgroup\$– nvdCommented Aug 11, 2015 at 14:44
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2 Answers
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If you realy want a complex solution with 3 555 chips: read the datasheet, configure all 3 as one-shots with a common trigger, one for 10 seconds, second for 20 seconds, third for 80 seconds. Use the first one to activate the first relay (resistor-transistor-diode) AND to disable the second relay (you could use a spare contact of the first relay for that). Use the 2nd one to activate the 2nd relay (unless it is disabled). Use the last one to disable retriggering.
Or: learn to program a microcontroller, maybe an Arduino is a good fit for your level.
If this is for a real product, any half-decent programmer can do this in any microcontroller, including the tiny 6-pins ones that look like a transistor and cost about half a dollar, like these:
answered Aug 11, 2015 at 15:42
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\$\begingroup\$ I never seen a microcontroller that looks like a transistor. Besides, transistors usually have 3 pins not 6. :P \$\endgroup\$– AlexxxCommented Aug 11, 2015 at 17:33
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\$\begingroup\$ Picture added. SOT-23 (with 3 leads) is a common housing for small SMD transistors. Small PIC and AVR chips in this housing add 3 more pins, but otherwise use the same housing (SOT-23-6). \$\endgroup\$ Commented Aug 11, 2015 at 17:37
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\$\begingroup\$ Right, transistors use 3 pin SOT23 not the 6 pin. Now correct... \$\endgroup\$– AlexxxCommented Aug 11, 2015 at 17:43
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\$\begingroup\$ I wouldn't use the SOT23 as it's a pain in the neck to solder or you need an adapter. An 8-pin DIP is lot lot easier to breadboard by the way. \$\endgroup\$– AlexxxCommented Aug 11, 2015 at 17:46
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\$\begingroup\$ That part of my answer was for a 'real product', not for a hobby project. \$\endgroup\$ Commented Aug 11, 2015 at 17:50
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555 Timers can only be triggered at one frequency with a specific duty cycle, there are many calculators online which will help you choose the proper components.
This is one I've used many times
As for the 60 second pause until the circuit can be retriggered, it would be easiest to use a simple microcontroller rather than a 555 timer to coordinate this. A 556 timer (which is essentially two 555 timers in one package) could conceivably be used as well.
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\$\begingroup\$ This is for a Halloween project that I'm trying to build and is my first foray into building a circuit. Relay 1 will drive a motor in one direction to move a prop to a location, and then relay 2 will move it back into position. From what I've learned 555 timers seem to be a good place for someone new to start. Thank you for your comments. \$\endgroup\$– StyxCommented Aug 12, 2015 at 4:09