555 Timer Problem - What am I doing Wrong?

[thelaughingfool]

For a while now, I've been trying to build a PWM circuit to control a motor. However, before that, I need to build a 555 Timer Circuit. And every time I try, it doesn't work. I've used about 4 ICs, so I doubt that's the problem. Provided are the schematic I used and a photo of my circuit. I've tried everything I can think of, and I can't help but feel like I'm missing something obvious.
Both resistors are 100K and both Capacitors are .1µf. I've used both a 3V and 9V battery on it.

**broken link removed**

 

[Audioguru]

A 555 can be used to make PWM but your circuit is missing the parts for it to make adjustable PWM. You simply made an oscillator.
The duty-cycle of the pulses must change to make pulse-width-modulation.
All datasheets for the 555 show how to do it.

 

[thelaughingfool]

Duly noted. I'll take that into consideration. In the mean time, I can't get even a simple 555 Timer circuit to work. If I'm lucky, my set up will dimly light up the LED. It's either not working, or it's flashing so quickly, I can't tell from looking at it. Mostly, it does nothing. I thought I was following the schematic as directed, so I'm not sure why it's not working. Can anyone tell what's wrong with my circuit as a 555 Timer?

 

[Audioguru]

The datasheet for the 555 shows that your calculated frequency is 48Hz which is too fast to see. The LEDs will appear to be continuously lighted but not at full brightness. A 555 is not strong enough to power a motor unless the motor is extremely small.

 

[BradtheRad]

The led's should alternate, as long as the output goes all the way to V+, and all the way to ground.
However this hookup could conceivably allow one or both to stay lit a small amount, even when it is supposed to be off.

It may help if you try disconnecting one led.

Also increase the value of the capacitor, in order to make the oscillations slow enough for the human eye to see.

 

[kabeer02]

Your circuit can not be used to control pwm its just a astable multivibrator, to control you pwm you need to control pin 5 of your 555.

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Your circuit can not be used to control pwm its just a astable multivibrator, to control you pwm you need to control pin 5 of your 555.

 

[myfaithnka]

I think you should adjust the resistor a bit.

You can use a preset here.

Another problem,if you are using a low current source. The ckt cant provide power to both leds and the motor.

For high power needs please add a transistor to the output of 555. (transistor as switch).