#### JulesP

Joined Dec 7, 2018
383

#### JulesP

Joined Dec 7, 2018
383
hi J,
Where did you get that post #37 circuit, its yuk!

This is LTS with just one LM338 to check out the design.
E
E, Your circuit only manages 4A whereas I need it to manage at least 30A which is why my attempt uses 5 x LM338s in parallel. Is that not a way to boost current capacity?

J

#### ericgibbs

Joined Jan 29, 2010
17,455
hi,
This is the important difference between yours and the posted circuit.
The Vinput is a 18Vac transformer, so 18V * 1.4= ~25Vpk less diode voltage drops.
To get a +12Vdc out the circuit must have at least 15Vdc to 16Vdc input.

E

Update:
Did you see this codicil.

Last edited:

#### JulesP

Joined Dec 7, 2018
383
hi,
This is the important difference between yours and the posted circuit.
The Vinput is a 18Vac transformer, so 18V * 1.4= ~25Vpk less diode voltage drops.
To get a +12Vdc out the circuit must have at least 15Vdc to 16Vdc input.

E
View attachment 228102

Update:
Did you see this codicil.
View attachment 228104
Yes I did and, given the language translation on the page I wasn’t overly confident in it which is why I drew it up and sent it for ‘review’.

So how might I construct a regulator type of circuit, as a more efficient alternative to the FET method, that can take my 12V, 25A and let me output 7-9V, 25A? Are there any off the shelf circuit designs I can explore?

J

#### crutschow

Joined Mar 14, 2008
32,090
I have a PWM power supply that has a nominal output voltage of 12V and a current capacity of 25A continuous.
Your diagram shows a PWM duty-cycle control.
Is that actually available?
Would it be possible to change the range of that control?
Do you have any information on what's inside that supply?

#### JulesP

Joined Dec 7, 2018
383
Your diagram shows a PWM duty-cycle control.
Is that actually available?
Would it be possible to change the range of that control?
Do you have any information on what's inside that supply?
I’m using a PWM from RMCybernetics as per the attached pdf and using a primary and secondary power supply as per page 5 of that doc. The reason for that is so I can deliver 12V to the PWM circuit and less than that to the electrolysis cell (ideally 8-10V) hence the need to construct a device to drop some volts at 10-25A.

The secondary supply is from:
inShareplus 12V 41.7A 500W, DC... https://www.amazon.co.uk/dp/B08GKTFJZF?ref=ppx_pop_mob_ap_share

and the primary PSU is a smaller but similar device: https://www.ebay.co.uk/itm/AC-110-2...-/203076666329?_trksid=p2349624.m46890.l49292

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