OY2L

Another great 16F628 project at this link 15x7 DISPLAY

Pommie

I need to set myself up with a website so I can post links to example code. It appears I was one of the few that posted (past tense) example code on this web site. Even the great Nigel posted links to his site.

Mike.

futz

I'm currently tinkering with something kind of similar. I have an 18F2550 controlling one bi-color (red/green) 5x7 LED matrix (like the one at the top there, but red/green). It uses a 74HC4017N to handle the multiplexing for the 10 columns.

In this pic I'm still missing two transistors (2N2222A) and haven't wired the 14 rows to the PIC yet.

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blueroomelectronics

That is some funky headsink on the LM7805

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Krumlink

I saw that, it must be 2-3 inches tall

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futz

Heh. More like 1-3/4" tall. Everybody seems to like that thing.

I have another with a big heat sink too:


And one with a Power Trends PT78ST105V buck regulator, rated at 1.5A

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AtomSoft

OMG those pictures are great (and the supplies )

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futz

You probably already know, but you can get those from HVWTech. The heat sinks you have to source yourself though.

One caveat with those power supplies: You have to pay attention to which end you plug them in on the breadboard. Only one end works with correct polarity. Plug it in the other end and it's backward. I just recently build a VERY busy breadboard and left room at the wrong end for the power supply. Plugged in the power supply and turned it on. No magic smoke was released, luckily, but I caught it almost right away.

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Sceadwian

Diode protection is probably not a bad idea in these kinds of supplies, the safety factor should outweigh the wasted power from the diode drop.

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OY2L

I have used this homebuilt supply on my Breadboard for a long time and never need a heatzink at all, never get that hot,

futz

Ya, my heatsinks aren't necessary. I just like them.

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olly_k

Surely in this case the only way you could give effective protection would be by putting a reverse biased diode across supplies (to negative) and therefore shorting the supply or am I missing an obvious solution here?

How about permanently marking the breadboard for a particular orientation?

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olly_k

Nice project you have reminded me I have got a corker of a future project, a board out of an old fruit machine with 36 5x7 display modules complete with some logic circuits to run the thing, must be serial data in but not sure how yet. I must attempt to work it out some day!

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futz

Wow! That's a ton of wiring!

I started out with two displays, but soon realized it was going to take all of those two breadboards just to fit the wiring for one. And it's not gonna be pretty!

Anyway, I'm having fun with it and learning some interesting things. My first schematic has already been trashed. It wouldn't have worked. Started building it and soon realized it was so wrong! So I'm happy that I didn't spend any more time on it than I did.

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olly_k

I forgot to add "and therefore shorting the supply should it be connected the wrong way round or am I missing an obvious solution here?"

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