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My first power supply

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MarkF:
You could also add a series resistor with the fan from the unregulated side (before the LM78xx's).  You will have to experiment a little with the resistor value to get the fan voltage down to 12V (and maybe 10 or 11 volts).  If the fan still puts out enough air flow, it will be a little quieter with a slightly lower than rated voltage.

Also since you are driving both regulators, the current capabilities of both the transformer and the rectifier bridge must be large enough for both (i.e. greater than 2A).  The capacitance of the filter cap must be large enough for both also.  You might actually be better off with two before the regulators.

Edit:  I just checked your first post.  The transformer output is only 12V CT @ 500mA. 
You are NOT going to get a lot of power from you supply. 
Watch that the combined output of both regulators is less than 500mA.

At 500mA and larger heatsinks, you probably do not even need a fan.

MarkF:

--- Quote from: OM222O on September 23, 2019, 01:53:23 am ---using a common mode choke followed with 4 capacitors and an inductor (2 large value electrolytics / tantalums and 2 small value ceramics) in a pi filter configuration should basically drop that switching noise to nothing  :-+ although I think the pi filter alone should be good enough in this case.

--- End quote ---

It is not a switching power supply.  A linear power supply with fan noise on the one output.

queennikki1972:

--- Quote from: MarkF on September 23, 2019, 02:00:03 am ---

Edit:  I just checked your first post.  The transformer output is only 12V CT @ 500mA. 
You are NOT going to get a lot of power from you supply. 
Watch that the combined output of both regulators is less than 500mA.

At 500mA and larger heatsinks, you probably do not even need a fan.

--- End quote ---

I upgraded the transformer to one I had lying around that is 1.8 amps, not 500mA since this is just an experiment for learning..

I learned from this project that I needed not only separate smoothing caps, but also at least 2 per side for redundancy. I will probably redo the entire main board to have separate caps and larger surface area for heatsinks.

queennikki1972:

--- Quote from: MarkF on September 23, 2019, 02:00:03 am ---You could also add a series resistor with the fan from the unregulated side (before the LM78xx's).  You will have to experiment a little with the resistor value to get the fan voltage down to 12V (and maybe 10 or 11 volts).  If the fan still puts out enough air flow, it will be a little quieter with a slightly lower than rated voltage.
--- End quote ---

I don't know why I didn't think of that!!!

queennikki1972:

--- Quote from: MarkF on September 23, 2019, 02:00:03 am ---
Also since you are driving both regulators, the current capabilities of both the transformer and the rectifier bridge must be large enough for both (i.e. greater than 2A).  The capacitance of the filter cap must be large enough for both also.  You might actually be better off with two before the regulators.

--- End quote ---

Bridge Rectifier is 6A and the one large cap is 6800uf . When I redo the new board Ill put 2x2200uf cap 35v per side.

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