PWM with digi-pot for heated gloves/socks?

[Tightwad]

Hello...I am an electrical tinkerer, with no formal training. For that reason my question may seem rather silly, but I am also willing to try anything. I want to learn how it all works, but that takes time....

I also have ADD (I am convinced) so I usually have 5-7 projects going at any one time. I just recently finished a PWM circuit for controlling fan speed on a computer. The circuit was fine, just bigger than I would like for my current project.

I would like to power and regulate a pair of heated gloves or socks individually. typically these are controlled together, but I might wish one hand/foot to be warmer than the other.

Total amp draw per glove is .85, at 13.5 volts (vehicle power). I would like to make a circuit that would be small enough to connect to the glove, and which would use a digi-opt with up/down switch instead of a rotary potentiometer.

I found this circuit, but I don't know enough to know if it can regulate the .85 amps needed:**broken link removed** (click on picture to go to relevant page)

Other questions:

where do the outputs of Q1 go? I see one is the ground side of the "lamp", but what does the black -> mean?

Sorry for the silly questions!

Tightwad

 

[Boncuk]

Hi,

you can make the circuit real small using an NE555 wired for PWM. It is just an 8-pin-IC and the MosFet transistor adds some extra room. Using a digital pot you should know if that circuit contains an internal switch debouncing circuit. (Otherwise the pot might "turn" too much.)

If you use a BUZ10 or BUZ11 they will suffice for your application. I made a motor byce handle heater system with 50W each and they perform well without a heatsink. They are just mounted to the metal of the enclosure which is air cooled.

To increase cooling of the transistors just bolt a small heatsink onto the enclosure.

I do not recommend to use the entire circuit in or on your gloves. Just make a small control box with two buttons and stow the control box at a place where it gets cooling air from the wind.

The black triangle underneath the MosFet is circuit ground.

Boncuk