Electronics Question

[Andy A]

Could someone with a good knowledge of electronics please tell me what potentiometer or variable resistor value I would need to alter the voltage from 0v to 12V on a sliding scale

 

[Dink]

lol what is the input voltage?

and if you need anymore than about 50mA of current it aint going to work

 

[sn00p]

What he said.

What you'll most likely want is a potentiometer & a darlington pair (or mosfet if you're into bigger currents), but without specifying your voltage & current requirements it's like asking how many fingers I'm holding up!

 

[LegoHead]

Could someone with a good knowledge of electronics please tell me what potentiometer or variable resistor value I would need to alter the voltage from 0v to 12V on a sliding scale

any value, just make sure you have the correct power rating.

http://www.electronics2000.co.uk/data/itemsmr/potdiv.htm

 

[Andy A]

sorry lads, its a computer power supply powering 3 fans, so 12 volts, I want a potentiometer so I can adjust the voltage to each fan seperately.

Don't say a fan controller, its for making a different project

 

[Dink]

you could get a couple of these

then build a circuit for each fan

 

[Andy A]

OK, how would you adjust them?? I would prefer somethin with either a slider knob or turn knob, they will need to be adjusted a lot and be fabricated through either a wood or abs plastic case

 

[Dink]

you would use a potentiometer to adjust them

 

[Andy A]

Now I'm confused, I thought the potentiometer is the resistor, thats what I have been using tonight, however I think its the wrong value becase all the voltage adjustment is within about 40 degrees turn of the 250 degree turn

 

[Dink]

there are two types of pot logarithmic and linear

sounds like you got a logarithmic one

 

[Andy A]

probaly so, so clearly now, what exact things do I need to adjust from 12v to 0v volts that I can make look pretty on a box

 

[Dink]

if you look here

gives you a circuit for 1.2-25v(will only be 1.2-12v if thats the input voltage)

just order those bits and some heat sinks for the IC and a blank stripboard and you should be away

 

[sn00p]

if you look here

gives you a circuit for 1.2-25v(will only be 1.2-12v if thats the input voltage)

just order those bits and some heat sinks for the IC and a blank stripboard and you should be away

Yes that would work, but there are a couple of things to be aware of:

- You've still not told us the current consumption of the fans! It's impossible to give you a reasonable solution without knowing this!

- Linear regulators are s**t, they get very hot. You might end up needing some very big heatsinks (but we can't tell without knowing your current requirements!). We've just done a project at work that used a linear regulator to power a bulb, the product has a second configuration with a fancy ultraviolet bulb and that bulb consumes 1 amp, we required a very big (far too big - if the IC gets too hot it goes into thermal shutdown) heatsink to dissipate the heat, so we're having to design a daughter board with a switching regulator because they have much better efficiency.

You should see the size of the heatsinks we have on our 40A current generator