So, I have been reading and trying to understand how a 555 timer properly works. Now, I still have alot to learn, but I think I am starting to understand it.
Here's a schematic I am working on.
I tried to keep the BOM line count down, that is why I chose 10K trimmer pots for both timers.
Here's how I am hoping the circuit works...
R2 would be adjusted to ~9.62k which should have the ON time of 666ms while R6 would be adjust to ~4.81K which should have an OFF time of 333ms on the first 555 timer.
R4 would be adjusted to ~4.81k which should have the ON time of 333ms while R5 would be adjust to ~9.62K which should have an OFF time of 666ms on the second 555 timer.
Now, I'm hoping it would display the flashes as this...
D9 | D10 | D11 | At Time Interval |
ON | OFF | OFF | 0 msec |
ON | ON | OFF | 333 msec |
ON | ON | ON | 666 msec |
OFF | OFF | OFF | 1000 msec |
At time 1000, the 12V supply to the timer circuits would be cut-off, do to the flashing relay (not shown) and then the circuit would just repeat/reset when the 12V switches back to the ON position at Time of 2000 msec.
The Relays need to stay off until the Timer triggers them.
Are my Values correct? Will this work?
16V, 25V, or 35V Capacitors?
1/2W, 1/4W, or 1/8W resistors?
1A diodes okay? Schottky or regular?
Since the supply voltage for the Timers are switched on and off continuously from a flasher relay......is there anything that should be done to help protect the Timers from any type of possible damage?
I don't have a simulation program, and I've tried using the LTSpice...I just don't understand it.
With my calculations (resistor values), I have duty cycles of 33.3% and 66.6%...from my understanding, the 555 timers don't perform well under 50%. what can I do about the 33.3% duty cycle from the second 555 timer? I'd like to try and keep the Trimmer Pots all at 10k, and the Caps at 100uF. That will keep my BOM Line count down. The calculation shows also that that both timers will perform at 1Hz.
I also read that the dip packages need to have a socket soldered to the PCB first, then the timer placed into the socket, as the heat from soldering damages the chip. I am guessing this is a stupid question but I am throwing it out there anyway....do the SMD version of the 555 timers have problems with the heat from reflowing?
I appreciate any help you guys can give me on this.
After I am done figuring out this circuit, I'll move onto another 555 Timer circuit, then maybe Ill get into Op-amps or something. I can't believe how many things can be done with 555 timers.