next topic »

[Reply #15 on:]

try rs http://uk.rs-online.com/web/p/led-display-drivers/6229493/ £7 (+VAT)
free delivery

10 is cheaper than 1? 

nb. that that's the surface mount version...probably not what most people here would want.

[Reply #16 on:]

£7 (+VAT)

At that price, it probably makes sense to program some AVR chips to emulate max7219.

[Reply #17 on:]

I am in no way affiliated with this seller.
I bought a tube of ten from this seller http://www.ebay.co.uk/itm/10pcs-MAX7219-MAX7219CNG-8-Digit-LED-Display-Driver-DIP-/140439183565?pt=LH_DefaultDomain_0&hash=item20b2d3e0cd a few months back. I tested them on a breadboard when they arrived an all worked without problem. The ones I have since used continue to work fine in clocks running 24/7

[Reply #18 on:]

£7 (+VAT)

At that price, it probably makes sense to program some AVR chips to emulate max7219.

They could do the multiplexing but it's quite hard to emulate current control.

[Reply #19 on:]

It already has a spi module. Make it into a slave. Once the spi received a byte, decide if it is the MSB, or LSB. If it is LSB, send the MSB+LSB to a local buffer (8x8), which will be processed by the display module automatically.

When I get some time, I will see if I can do it.

[Reply #20 on:]

I am in no way affiliated with this seller.
I bought a tube of ten from this seller http://www.ebay.co.uk/itm/10pcs-MAX7219-MAX7219CNG-8-Digit-LED-Display-Driver-DIP-/140439183565?pt=LH_DefaultDomain_0&hash=item20b2d3e0cd a few months back. I tested them on a breadboard when they arrived an all worked without problem. The ones I have since used continue to work fine in clocks running 24/7

I bought like 50 of them from Tayda and have used 12 and all have worked, that is why I recommended them,.  I also am in no way affiliated with them except I lile Pad Thai.

[Reply #21 on:]

Last time I bought some I paid $12 for 10 chips (shipping included) and they took about a week to arrive. They came in Maxim-branded tubes and powered on just fine.

Update: I had some 100% genuine Maxim chips in my hands yesterday and compared them.

"Maxim" tubes or not, the eBay chips are different. They're about 3mm shorter and the legs at either end are only a half-leg. The Maxim chips have a full leg as shown in their datasheets.

(See the image on this auction to see what I mean by "half-leg": http://www.ebay.com/itm/290760288578 n.b. that's not the same seller, it's just an auction picked at random because it has a nice picture...)

I also got half way though the tube and found one that didn't work. I don't really mind ... I'm only using them for hobby stuff and I can afford to throw a couple away at eBay prices. It's something to bear in mind if you're using them for mission critical applications though.

[Reply #22 on:]

Max7219 is really old and I would be surprised if anyone uses them in production. Whatever you get off ebay is likely clones.

[Reply #23 on:]

For one-off stuff, it is a lot easier to make your own clone from a mcu.

[Reply #24 on:]

For one-off stuff, it is a lot easier to make your own clone from a mcu.

How does an MCU do current regulation?

Even if they're clones they still save a lot of work/components.

[Reply #25 on:]

How does an MCU do current regulation?

Exactly the same way you would use a mcu for current regulation? Like using a comparator, using adc, or pwm?

Even if they're clones they still save a lot of work/components.

vs. what?

[Reply #26 on:]

Even if they're clones they still save a lot of work/components.

vs. what?

They have current regulation, multiplexing, serial interface, etc. in a single 24-pin DIP. What MCU will do that with no external components?

[Reply #27 on:]

What MCU will do that with no external components?

A mega328p for example?

[Reply #28 on:]

What MCU will do that with no external components?

A mega328p for example?

How would you set 20mA current for the LEDs?

[Reply #29 on:]

As you would otherwise, with resistors, comparators, adc, etc.

Or you are looking for something else?