the output I need is the max rating of my lm2576 stepdown; so I don't know what I need, but with 36V I can have all voltages between 36V and almost 0V at 3A (I think)

 

You will have to change the pot to 35K, inductor will have to be changed since it was calculated for 12V max.

 

I'm wary of adjusting a R600 device. Not only does that power supply exceed my budget by about ZAR200, shipping is going to add another ZAR200-300, so no, not an option
the cheaper one is withing my budget, but probably not after shipping

FOUND IT:
http://www.mantech.co.za/ProductInfo.aspx?Item=372M0368

350 WATT SINGLE OUTPUT ENCLOSED SWITCHING POWER SUPPLY
INPUT: 90-132VAC / 180-264VAC OUTPUT: 36VDC @ 9.7A

This is probably a stupid question, but will this power supply take 230V MAINS power just like that?

 

Yes,its selectable.

 

No I'm not trying too non-appreciate your contribution ISB123, but the datasheet have 0-40 input and no change on the inductor, only changes in R1 and R2, I'll accept that the datasheet provide a standard setup, but then if the datasheet is wrong, please show me the calculations for calculating the inductance

 

You would need 150uH.

 

the next value up from 100uH is 220uH, would that work? And how do you calculate the 150uH?

EDIT: I can get 150uH at Mantech, where I'll be buying the 36v PSU so if I need specific value then I can get it
EDIT2: what amperage do I need?
3: I can also get 47uH and 100uH from fort777.co.za

 

See page 15.
http://www.ti.com/lit/ds/symlink/lm2576.pdf

Use 100uH and 50uH in series to get 150uH.They should be rated for 3A since that is max. current output.

 

these are the fort777.co.za ones, they would limit the output to very low levels?


IND220 410
IND101 275

the 410 are
IDC(mA)
(max) on the 220uH
and 275 on the 100uH

Mantech: http://www.mantech.co.za/ProductInfo.aspx?Item=72M2334 is:
IND RAD W/W 150uH 4A 0E098

^\-this what I need? it's R20 for one, and the fort777.co.za ones are R1.12
I'll Pay R20 for one, no problem

 

Buy one from mantech,fort777 ones will overheat.

 

3x +V connectors, that means I can run 3 Voltages simultaneously? That'll be cool. And the ground Neutral and Live connectors mean I have to use the bare wires of a mains cord with my own plug for the wall? Now they should just have stock...

this doesn't require a external transformer does it? No, it says VAC, duh

EDIT what would happen to the stepdown psu as a 12V input psu if it has 150uH and not 100uH?
EDIT2: moved this question to it's own thread http://forum.allaboutcircuits.com/threads/inductance.104399/