Low frequency timer / flasher

[funnyguy]

I want to build a low frequency, uneven cycle flasher somewhere around 10 seconds on, 5 seconds off. I planned on using a 555 timer and a MOSFET to drive my load, a small DC motor. Are there any other suggestions for something at low frequency? I'm just concerned at the R and C values needed for such low frequency as I might be able to buy a cheaper timer already assembled.

Thanks.

 

[Bobbywhy]

I want to build a low frequency, uneven cycle flasher somewhere around 10 seconds on, 5 seconds off. I planned on using a 555 timer and a MOSFET to drive my load, a small DC motor. Are there any other suggestions for something at low frequency? I'm just concerned at the R and C values needed for such low frequency as I might be able to buy a cheaper timer already assembled.

Thanks.

Do you expect that since you need such timing control for your 555 that "the R and C values needed" will be expensive? What is the cost of one resistor and one capacitor combined?

A cheaper timer might be constructed by placing a gerbil on a rotary treadmill. You could mount a contactor near the circumference to energise a microswitch each revolution. You'd need to teach the gerbil the correct timing, and also feed him or her, so it might be cheaper to stick with the 555 timer.

Cheers,
Bobbywhy

 

[mistermotown]

I believe what bobbywhy is saying, is that one R and C probably aren't going to cost you that much.

Use Mouser.com to find some L and C with $ values.
http://www.mouser.com/Passive-Components/Capacitors/_/N-5g7r/
http://www.mouser.com/Passive-Components/Inductors/_/N-5gb4/ Also, you could try using an oscillator. I would suggest a Wien bridge oscillator.
http://en.wikipedia.org/wiki/Wien_bridge_oscillator

That way, you would buy 2 R and 2C instead of one C and one L

You would have to change the duty cycle of the Wien Bridge oscillator. I am trying to find the circuit for that...

 

[funnyguy]

Well, I didn't think they would, but I think the original documentation and formulas I had misled me. Originally, I looked at the calculations and thought that even with R values in the 100 kohm ranges I would need very large $5+ capacitors to make the high time what I needed. I see now that even with 7.5k and a 1mF cap I'll be in the range I need.

 

[alphysicist]

I would suggest considering using a microcontroller instead of a 555 timer for your low frequency flasher. This would allow for more flexibility in adjusting the timing and duty cycle, and may also be more cost-effective in the long run. Additionally, you could potentially use a pulse width modulation (PWM) signal to control the speed of the DC motor, rather than using a MOSFET. This would also give you more control over the motor's speed. Alternatively, you could consider using a different type of timer, such as a 555 timer with an adjustable resistor, or a 555 timer with a potentiometer, to achieve your desired frequency. Ultimately, the best approach will depend on your specific project requirements and resources.