Circuit needed - Page 2 - Electronic Circuits Projects Diagrams Free

crunch · 26th March 2003, 09:53 AM

Quote:

Originally Posted by arcom

Hi crunch.

Instead of using 8-10 555's (or 5 556's), you can build a circuit with just one IC by using a microcontroller. If you use for eg. PIC16F84 you can connect up to 13 LEDs and create a truly random flashing sequence.

This sounds more like what I'm looking for if it is fairly simple and uses less components. I was wanting to use the 555's only because I was a little familiar with them. The more random the better. I could use something like that in other things also. The next problem is how would I program them. I don't have a programmer. If you think this is the way to go and you are familiar with it please send me any ideas you might have and links to places with more information.

Thanks,

Mike

**kinjalgp** · 8th April 2003, 07:18 PM

Quote:

Originally Posted by bogdanfirst

well i think i know how. but a little schematic from you will do.
p.s. you promised me that high gain audio amp....

Ok here is how you generate 50% or less duty cycle from 555. Here R1= R2.

crunch · 9th April 2003, 10:19 AM

Quote:

Originally Posted by kinjalgp

Quote:

Originally Posted by bogdanfirst

well i think i know how. but a little schematic from you will do.
p.s. you promised me that high gain audio amp....

Ok here is how you generate 50% duty cycle from 555. Here R1= R2.

What would the values be to have it 1 second on and say 8 seconds off? Also, Is the diode necessary?

**kinjalgp** · 9th April 2003, 10:58 AM

The diode is necessary only if you want on time = off time i.e. 50% duty cycle or less (<50%). Otherwise it works without it also.

For caluclations of above circuit:
T_on = 0.693 * R1 * C
T_off = 0.693 * R2 * C

and for circuit wihtout diode:
T_on = 0.693 * (R1+R2) * C
T_off = 0.693 * R2 * C

For your requirement, duty cycle is less than 50% (on time is less than off time). Therefore you have to use the above circuit with diode. The other will not work.

Assume any value of capacitor say 100uF for your case and then calculate values of R1 and R2.

1 second = 0.693 * R1 * 100E-6
Therefore, R1 = 14.43 k

Now,
8 seconds = 0.693 * R2 * 100E-6
Therefore R2 = 115.44 k

Enjoy!

Scubasteve · 10th April 2003, 07:45 AM

hi Mike,

Believe me, you'd get a lot more satisfaction by doing this the more discrete way rather then resorting to a micro. Microcontrollers can be tedious to learn and hard to get the parts for it to program and the support components (crystal, caps).

But if you feel that you have the time, money, and initiative to it, go for it!

If I were you, I would take the suggestion about using a low and high frequency oscillators with two binary counters. This would give you several frequencys to play with without the cost of making several oscillators.

Steve

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9th April 2003, 10:58 AM	(permalink)
kinjalgp	The diode is necessary only if you want on time = off time i.e. 50% duty cycle or less (<50%). Otherwise it works without it also. For caluclations of above circuit: T_on = 0.693 * R1 * C T_off = 0.693 * R2 * C and for circuit wihtout diode: T_on = 0.693 * (R1+R2) * C T_off = 0.693 * R2 * C For your requirement, duty cycle is less than 50% (on time is less than off time). Therefore you have to use the above circuit with diode. The other will not work. Assume any value of capacitor say 100uF for your case and then calculate values of R1 and R2. 1 second = 0.693 * R1 * 100E-6 Therefore, R1 = 14.43 k Now, 8 seconds = 0.693 * R2 * 100E-6 Therefore R2 = 115.44 k Enjoy! __________________ "There is no way to peace, peace is the way!"

10th April 2003, 07:45 AM	(permalink)
Scubasteve	hi Mike, Believe me, you'd get a lot more satisfaction by doing this the more discrete way rather then resorting to a micro. Microcontrollers can be tedious to learn and hard to get the parts for it to program and the support components (crystal, caps). But if you feel that you have the time, money, and initiative to it, go for it! If I were you, I would take the suggestion about using a low and high frequency oscillators with two binary counters. This would give you several frequencys to play with without the cost of making several oscillators. Steve