Yes, I'm thinking a 3 amp 'brick' would be good for a display with 10-ma "average" current for each LED (2.5 amps total "peak" current). That should be magnitudes brighter than what you're getting now. And if you should happen to find a 5 or 6 amp supply the extra capacity won't hurt.

The LM350 adjustable linear regulator would be used to power the display portion of the project with the 12 to 15 volt power 'brick' as the input to the regulator.

If you get a 5 amp supply and you want a 5 amp variable regulator then perhaps you should look at the adjustable version of the National LM1084 series (or other manufacturers) regulators.

 

OK. I understand a bit more now.

Should I use the SX52 protoboard 5vdc 1 A power for the SX52, all the logic chips, etc..? Does it make sense to also get a 5vdc regulator like you mention to power the logic chips? Wilf made it sound like in him last posting that the 5vdc 20A should not be used for the logic chips - that is why I am asking (but then this is much less than 20 A {being 3 A or 5 A})

I like the idea of getting as much current as possible - just in case I want to expand on this design in the future and need more current. I did have a hard time on Google locating any adjustable regulator more than 5 amps. I will let you know what I can find.

How will this new power supply connect to the rest of the circuit? Is it only connected to the P-FETs along with a common ground and decoupling caps, etc.?

OK - Now what is the final list of components I will need to buy.

 

Yes, that will isolate the two supplies and your logic circuitry should enjoy clean glitch free power.

No, I only mentioned that I would be throwing a 5v regulator on my 'test' board while I experiment and play with that LM350.

I agree, that's a good idea.

They're out there, I just haven't had the opportunity to use them yet and so I can't make a recommendation. Sorry.

Yes. The new supply will power the new adjustable regulator which will power the display through the anode switches. You'll adjust the pot' on the adjustable regulator PCB to set the regulator to the correct voltage for full brightness.

Samples?

I haven't found a source for sampling ULN2803's or MIC5821's but I did get some Allegro A6821 samples without any trouble last year (the A6821 is a pin-for-pin compatible MIC5821).

I ordered samples of the adjustable versions of the 3-amp LM350's (TO-220) and the 5-amp LM1084's (TO-220) from National a short while ago without any trouble.

I ordered and received Fairchild FDN304PZ samples about a year ago.

 

Also please note that Murphy's Law suggests we'll find the flaws in the current design that will require changes to the parts list or bill of materials immediately after you order and pay for those parts (grin).

 

Did you know about:

www.findchips.com

It will list all the vendors / distributors for almost any part you need. This is how I knew that Digikey sold the MIC5821.

Do you know if I can get free samples of these? If not it is ok but just thought I would ask.

 

I already said two messages ago that I had not found a source for sampling MIC5821's but I was able to sample the Allegro version of the MIC5821 (the A6821) from Allegro.

 

Thanks Mike. I wasn't clear if you meant the samples were free or not. I just ordered 6 free samples of the Allegro A6821SA-T. I have seen some vendors that have Samples but they are not free or at a partial shipping cost or something.

 

Yep, you're right. I just got the order confirmations from National for the regulator samples and they wanted $18.00 so I cancelled the orders.

Bummer!

 

I just ordered 10 free samples (max) of the Fairchild (2.4 A) FDN304PZ. I need to find another source to get 10 more. I will look.

 

Wait a few days and order again (grin).

BTW, I also received samples of the following parts from Fairchild long ago;

PN2907A (TO-92)
2N4401 (TO-92)
2N4403 (TO-92)

LM2931A, 5v, 100ma, LDO regulator (TO-92)

 

Thanks - I thought I would have to wait a month or so.

ALSO you mention Q3 and Q4 earlier. Do I need to get 20 of each?

 

You're already working on collecting the 16 or 32 P-channel FDN304PZ MOSFETs, right? If so and if you think you're going to end up using a higher voltage supply for the display, then you probably want to order some 2N7000 N-channel MOSFETs. I use these so much (relay drivers, etc.) that I ordered 100 of them from DigiKey a couple years ago. They sent me ones with preformed legs on tape and when I called to explain that I ordered loose ones with straight legs they gave me a refund and told me to keep the ones they sent me by mistake.

 

Mike,

I bought some PN2907A FETs (800mA), 2.4 amp Fairchild FDN304PZ P channel FETs AND 2N7000 N-channel MOSFETs on Mouser.com too.

As a side note, I received some UDN2982A-T samples from Allegro Microsystems. These appear to be 500mA output drivers similar to the ULN2803 (but not inverted).

Can these or should these be used in the design instead of the P channel FETs.

BTW: I borrowed a new Fluke meter from work to confirm my home meter reading on the current taken the other day from my 16x16 LED matrix (display 2). I got readings from 2 mA to about 45 mA. This is not much of a draw when using a 2 A 5vdc Power Supply into Vin on the SX52 protoboard.

Thoughts about this new information...

 

Mike,

Wilf posted a new message and circuit (using a TIP32C) 3A power transistor (that I did not buy) and MORE UDN2803s.

He did say that the 5vdc 20A power supply is just about right for the voltage levels needed.

http://www.ts1000.us/cgi-bin/yabb/Ya...63;start=15#15

 

Well I hope the 5v supply works out. I feel very guilty about you purchasing it and our misunderstanding (I had meant cheap surplus higher voltage and higher current laptop supplies).

I wish I could have talked you into that 1/8th (12.5%) duty cycle design because I've verified that it can provide more than full brightness (grin) from a 5 volt supply.

Up to now I've only bread-boarded a couple 8x8 modules to verify hardware and software but I'm looking forward to making PCB's for a modular 8 module Clock/Calendar. Here's one idea I had (below) but it would require removing all of the modules from the aluminum frame if I had to replace a module. So instead I think I'm just going to have a single dual row 20-pin header on each module and use a 20 pin IDC cable connecting each module on the back side of the aluminum frame. The 5 volt 1.5 amp regulators on each module will be running well under their rating and should generate less heat than a big honkin' 8-10 amp regulator located somewhere else running everything.