Need help modifying a transistor flip-flop circuit

[MillenniumFalsehood]

I'm trying to create a pulsating circuit, and I think I can take a transistor flip-flop design, hook up one end to a small string of LEDs, then the other end to the same string but with a larger current-limiting resistor as well.

I'd like to know if there's an online calculator where I can input certain values for resistances and capacitances and get a flash rate. I've seen something like this for the 555 timer, but I don't need a flasher.

[Mr. Engineer]

The only flip-flop circuit I can think of, without having to use a 555, would be this one:

http://talkingelectronics.com/FreeProje ... mplete.gif

And here is the link I got:
http://talkingelectronics.com/FreeProje ... age16.html

[MillenniumFalsehood]

Yeah, I got that page on my first Google. Thing is, I'm trying for a flash rate of about 600 flashes per minute (10 per second), and I'd like to know just what values to use to achieve this rate.

I'll try experimenting. Couldn't hurt, could it?

[Mr. Engineer]

Hokay, lets try this, but I think I am quite rusty on this and I could be very wrong:

I think the formula is f= 1 / (0.693 (R3*Q2 + R2*Q1), where the R2, R3 are the 10K resistors from the diagram above.

And assuming that: R = R2 = R3, Q = Q1 = Q2 values, the formula is now:

f = 1 / (1.38 * R * Q)

At 600 flashes a minute or 10 flashes a second, the frequency, f is 10. So,

10 = 1 / (1.38 * R * Q)

R * Q = 1 / (10 * 1.38)

R * Q = 1/13.8
R * Q = 0.07246

Let's make Q to be 1uF and so, R will be 72K. Or, if you want the Q1 and Q2 to remain at 100uF, just like the circuit above, then the Resistor values R2 and R3 will be 720 Ohms.

[MillenniumFalsehood]

Thank you very much! I'll try this out as soon as I get another Klingon Bird of Prey on the bench.