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Old 31st March 2006, 06:01 PM   #101
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Just because there is a spot for them on the board doesn't mean you can't run leads out to front panel LEDs. For that matter, there is no reason that the LEDs are required if you have some other power on indication.

Good idea for a single trim pot.

Speak up, the rest of you!
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Old 31st March 2006, 06:29 PM   #102
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I mailed Bob a set of PDFs.

Bob please post them after review and let everybody rewiev and ok the data for production.

Thanks

\Jens
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Old 31st March 2006, 06:40 PM   #103
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I'll post the files shortly - they are too big to attach so I need to do some work on them.
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Old 31st March 2006, 07:55 PM   #104
kro5998 is offline kro5998  Netherlands
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Bob,how much current did you draw while testing the psu?
Looking at Jens's pictures the caps for C4,C5 seem very small.
If they are only 680uf they are too small for the current you drew.
Checking out dimensions for Panasonic FC's you could go as high as 3900uF per capacitor.This would lower the ripple significantly.
I personally will put the biggest capacitors that will fit on the board.

When using a 18 V transformer the voltage of the caps should be upgraded to 35V.

kro5998
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Old 31st March 2006, 08:05 PM   #105
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What is the size and voltage rating and price of the 3900F caps?

I have not looked close to find the biggest cap that would fit, but if anyone has suggestions to parts that fit the current board, please step forward so the BOM can be updated.

\Jens
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Old 31st March 2006, 08:12 PM   #106
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I'll let Jens answer the question about current draw during testing, as I have not built my prototype yet.

We could go up to 2700 uf / 35 V in the same 16mm od form factor. That increases the cost of the parts kit by $4.25.

Comments on increasing the cap value?
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Old 31st March 2006, 08:16 PM   #107
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Caps: The bigger the better.

I used 2 x 470 F during the testing (what I had in my box of caps)

\Jens
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Old 31st March 2006, 09:12 PM   #108
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I simulated the main filter with PSU designer. Even with 2700 uf-1R-2700uf, there is barely enough voltage for the regulator to work at 500 mA using 15V input. We need the next standard higher voltage transformer, 18V.

With 18V input and 680 uf, we end up with 3.5V of ripple going into the regulator at 1 amp, and about .75V for the regulator to work - the bottom of the ripple is 17V. at 1 amp. The ripple stays above 20V at .5A, so this would do for a light load economy version.

At 1200 uf in the CRC the 1 A ripple drops to just under 2V and the bottom is >18V. The .5A ripple stays above 20.5V

At 2700 uf CRC, the 0.5V ripple stays above 17V up to 1.5A output.

I think a good compromise is to bump the kit capacitance to 1200 uf. The resulting PSU will be suitable for 1 amp output up to 15V. This will only increase the parts kit cost $1.50, instead of the $4.25 for 2700 uf.

Comments?
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Old 31st March 2006, 09:14 PM   #109
kro5998 is offline kro5998  Netherlands
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As we stay with the 15V transformer we can go to 3900uF in the same form factor.(EEUFC1E392L)

As the ripple is proportional to the current we don't know for shure until tested.

For me personally the 15V will do with the biggest possible caps since i will only power two filter boards.

Jens,did you measure the voltage drop over R1 and the pass device?
3 to 5 V over the pass device should be more then enough for proper regulation.Perhaps you can decrease the size of R1.

kro5998
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Old 31st March 2006, 09:48 PM   #110
kro5998 is offline kro5998  Netherlands
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Sorry Bob,you posted the same time i did.
I did some simulations on my situation and when using schottky's (1N5819 or 1N5822) i can do with a 15V tranny.
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