Hi. I made a simple speed controller with a 555 timer. (just using variable resistor to control duty cycle, a ghetto-PWM)
Though it's simple and works fine, I know I won't be able to run anything with high current on this setup since the 555 timer has it's limitations so I decided I would use the output to drive a high current transistor. There's a problem though, I'm using the discharge output (pin7) which shorts the caps to the ground, which means it's going to be the negative output. The NPN and PNP transistors I have both require positive voltage for the base. (tip31a, tip42g are the two I have on hand)
I'm fairly new to electronics but I know most of the basics. Any help or anything pointing me in the right direction would be greatly appreciated. I know there are some simple speed controllers out there using mosfets but I would really like this one to work out mostly because I don't like to give up if there's a possible solution.
Thanks for your time!
Oh and here's a link to the schematic I used:
pwm.png (image)
Though it's simple and works fine, I know I won't be able to run anything with high current on this setup since the 555 timer has it's limitations so I decided I would use the output to drive a high current transistor. There's a problem though, I'm using the discharge output (pin7) which shorts the caps to the ground, which means it's going to be the negative output. The NPN and PNP transistors I have both require positive voltage for the base. (tip31a, tip42g are the two I have on hand)
I'm fairly new to electronics but I know most of the basics. Any help or anything pointing me in the right direction would be greatly appreciated. I know there are some simple speed controllers out there using mosfets but I would really like this one to work out mostly because I don't like to give up if there's a possible solution.
Thanks for your time!
Oh and here's a link to the schematic I used:
pwm.png (image)