[diablo9]

I feel having a variable output wallwart will be very handy when testing the new assembled gears. a DC wallwart with 5V-24V with 2V increments will be very nice, any recommendation?

 

[skyskraper]

something like this is what you probably want. im sure u can find a similar non expensive kit in the states

http://www.altronics.com.au/index.as...=item&id=K3200

 

[DaKi][er]

Diy one

Get some generic wallwart, add in an lm317 adjustable regulator with a pot to change the voltage out, add on a voltage pannel meter if you want, a few output terminals of your choosing and you got yourself a basic bench psu just about

 

[diablo9]

Quote:

Originally Posted by DaKi][er Diy one Get some generic wallwart, add in an lm317 adjustable regulator with a pot to change the voltage out, add on a voltage pannel meter if you want, a few output terminals of your choosing and you got yourself a basic bench psu just about

It looks like TREAD is a good point to start with.

Quote:

You could jumper across R2 and just put a 2.5K pot here to get full adjustment from approximately 1.5V to 32V, but these trim pots are not designed to tolerate frequent adjustments.

So I basically use a wallwart with TREAD and jumper R2, put 2.5K POT at VSET position, right? I guess I will need a single channel POT, or just Pana EVJ/ALPS and just use half of it?

I thought slider POT instead of rotary POT could be better for my purpose, I found two options in Mouser catalog:
http://www.mouser.com/catalog/624/489.pdf
http://www.mouser.com/catalog/624/494.pdf

And in the options for slider POT, what does audio taper and linear taper mean? different resistor value/travel length curve?

 

[skyskraper]

put 2.5K POT at VSET position, right? I guess I will need a single channel POT, or just Pana EVJ/ALPS and just use half of it?

you can use any old pot, single channel. no need to worry about audio considerations that most pots mentioned here work with. the cheaper the better screw the panasonics and alps for this application. an alpha pot kicks arse for audio itll rip more then enuff for voltage reg adjustment.

And in the options for slider POT, what does audio taper and linear taper mean? different resistor value/travel length curve?

i would go with a rotary pot. the mechanical resistance of rotary pots i've found to be tighter and with something like this you would not have to worry about nudging it as much.

audio taper is a logarhythmic resistance taper that roughly matches the manner in which the human ear responds to volume changes. a linear taper does not work as nicely in the same volume application.

i am working on a mixer right now. the longer the travel for the same resistance the greater the effective mechanical resolution. although this is a moot point mostly when you are considering variable resistors for a voltage regulator.

 

[diablo9]

the thing is: I don't even have any "old cheap POT", so I guess I'll just use the cheapest rotary POT that I can order from Mouser.
Although Tangent mentioned 2.5K POT, I guess any 1K or 5K POT should work and giving wider/narrower voltage range.

 

[DaKi][er]

Quite easy to work out, the output voltage being = 1.25(1 + R2/R1) (I don’t know the resistor names tangent used, R2 is from adj to ground and r1 from v_out to adj) work out the output you'll see when set to the lowest setting of your pot (0ohm) and the highest setting and you have the output range

Also you want the pot to have the most range out of it you can, where at the highest setting you just reach the highest output voltage you can get, so without the diode bridge on the tread you want the pot at the highest setting to output 2v less than the voltage output of your wallwart
Seeing you can’t really change the pot value real easy as the value of them jump quite far between them, change the other resistor to fine tune it to where you want

And you want a linear single gang pot

Also this is a great opportunity to skip the premade pcb and learn how to make one up yourself on protoboard and p2p