The voltage on the input is probably going to be higher than 24.5V - and in any case, it's NOT a regulated supply, so if it drops a bit under full load at full voltage, it doesn't matter
Funny, I thought it was supposed to be a regulated supply. Even if the voltage is higher than 24.5V, say 30V off load, it certainly will drop below 26V when a load is connected and the ripple valley will be even lower, probably about 18V.
Suggesting you move from an 18V to a 36V transformer is ludicrous, will blow the capacitors up, and massively overheat the regulator.
I didn't suggest that.
I'd suggest using a 30V untapped transformer with a bridge rectifier and 50V capacitors.
While you were 'looking carefully' did you not read the discussion of the transformer?.
I admit, I didn't read it before but now I have, I can say it's inadequate because it doesn't discuss peak voltage, dropout, ripple, current rating, and filter capacitor sizing; all important things to consider when selecting a transformer and filter capacitors.
Thanx for all the replies if you guys say it will not work then I am not going to build it, HERO999 recommended a lm317 based psu. That would be fine all I am wanting is a stable dc power supply that I can adjust the voltage and current from something like 0-20V and 0-2A. those numbers are not set in stone I just want around that and have pretty fine control of the current. If any one can supply a schematic for this that would be VERY appreciated.
The LM317 will nearly do that.
The maximum current rating is 1.5A but I've had no problems drawing 2A for extended periods of time. the datasheet says the the current limit varies between 1.5A and 3.4A, 2.2A is typical but don't bet on it. The current can also be boosted by adding another transistor or more.
The current limit is fixed between 1.5A and 2.2A but can be made adjustable by adding a couple transistors.
The minimum voltage setting is 1.25V but it can be reduced to zero using a band gap reference or an op-amp.
https://www.electro-tech-online.com/custompdfs/2010/03/LM117.pdf
It depends on what you want.
How important is:
Operating down to 0V?
Having an adjustable current limit?
Being able to supply 2A rather than 1.5A?
As previously mentioned, it's possible to do all of the above, with additional components.