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Need tips on building a variable power supply

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jah118:
Hi fellows

I am trying to build a variable power supply, with an adjustable Current Limiting feature.

I have an old schematic on a design of a variable power supply(first attach), using a lm301 as the ic

with that schematic in mind i tried to make my own, but i have to replace some components, because i will be using a transformer  with an output of 30v 10A, i and i am afraid when the
parts arrive, it will not work because of my inexperience.

so my first draft of converting the schematic to fit my requirements(because of the one i am basing my design off, is only up to 2A):

2 boards in one unit, which can handle up to 5A each and adjust its current and voltage. So i have 2 small power supplies in one box.

with that in mind, and i have no idea how get current limiting part to work as intended. i decide to just make a schematic for the voltage regulating part,
but i have kept the current limiting part, by adding a screw terminal with the output needed to wire that section to voltage schematic. while i figure out to get right values and parts for the  current limiting part.

first draft of a schematic (second attach)

when i made the first schematic i did not take into account, how to cool the 3055 transistor, so with that in mind i have changed it for a screw terminal, and brought a large heat plate for it to be mounted in.

so redid that part an have now made a new schematic, with a board designed that is maybe ready to be ordered ordered.(last 3 attach )

is there any thing i can improve on, or does anyone have an idea to what part i need for the current limiting part, my main problem with it, is that Resistor6 and resistor 7, is the hard part, beacuse
how big does the effect Resistor(6) need to be to handle the full load. And how would i make a circuit, that short its self so i can set the max current there can be drained? after it has been set.   


Thanks :)

mvs:
Do you wish to built your own design, or it is ok for you to use some DIY Kit?
On ebay, aliexpress and some other chinese shops you can find 30V 3A kit for linear power supply (pcb + components) for around $5. It is based on TL-081 opamps, schematic is in attachment.

https://www.aliexpress.com/item/DIY-Kit-0-30V-2mA-3A-DC-Regulated-Power-Supply-Continuously-Adjustable-Current-Limiting-Protection/32903085230.html

David Hess:
10 amps at 30 volts is beyond what a single power transistor can handle reliability without fold-back current limiting; 20 volts at 1.5 amps would be more realistic so I suggest building a lower power supply to gain more experience first.

The design as shown is certainly workable although the current limit is pretty basic.

mvs:

--- Quote from: jah118 on November 23, 2018, 04:33:56 pm ---i will be using a transformer  with an output of 30v 10A

--- End quote ---
You mean 30V AC RMS? It is too high for both designs. After rectifier it will be >40V. Power supply limit of LM301 and TL-081 is 36V, and you need also acount for negative supply rail (2.7V or 5.1V) and some safety margin.

wasyoungonce:
Jah...do you have a link to the original PSU page?

Thanks

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