Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

12vdc fan controller

Status
Not open for further replies.
Sceadwian said:
Make sure it's rated for the wattage it's going to be wasteing or it's going to get awful hot.
A 10k pot across the 12V supply will dissipate (12 squared)/10k= 14.4mW which is nothing.
The fan draws 0.5A at 12V. If the pot is set to halfway then fan's current is about 0.25A.
The TIP31 transistor has a typical current gain of 160 so its base current is 0.25A/160= 1.6mA. The 1.6mA in the pot with 6V produces a dissipation of only 1.6mA x 6V= 9.6mW which is nothing.

If the transistor has current gain near its allowed minimum then the pot might get slightly warm.
 
So how would i use the 10k pot?
 
Make the circuit like this:
 

Attachments

  • Fan.PNG
    Fan.PNG
    4.7 KB · Views: 210
audioguru said:
Make the circuit like this:
It's too bad he doesn't have a 1K pot. The 10K pot will tend to cause the fan to only really start to work in the top 25% of the pots rotation. Using a darlington transistor will give better results at a sacrifice of 0.7V less at the max setting.
 
Thanks audioguru. It works great. Now i have to go find a TIP31(i am using a 2n2222, it doesn't like the heat...) How do the nice one's do it?, like the one i have pictured on the first post?
 
how do the nice ones do what?

the expensive ( i dunno about nice ) fan controllers still have transistors, and they still get hot ... some of 'em saddle a poor rheostat with the burden instead, those don't often last too long.

or they cheat and use pwm, and then you're back to the beginning of this thread with pwm not being the optimal solution.
 
Screw it! The mod didn't turn out. The lucite cracked, and now the thing looks like crap.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top