Failed to get this digital clock kit working :(

From the original schematic it appears that the common cathodes are connected to one pin of the chip, so if all 8 segments are lit this pin is required to sink 8* the current of the driver pins. When I've used this type of display there has been a transistor twixt common cathode and chip.

I could well have misread the schematic of course

Edited By duncan webster on 11/05/2021 20:25:02

Thanks for the good thought, Ian

I suspect that the processors may not have been programmed [or are not programmed correctly] but I have no way of checking, and am not much inclined to pursue that side of things.

There were absolutely no instructions, or-logic of-operation, provided with these kits ... so not much educational value. ... But at least they were very cheap.

MichaelG.

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For anyone who might have these ^^^

This appears to be another model from the same series [but lacking the clock colon]

**LINK**

https://theokelo.co.ke/how-to-get-your-hs420361k-32-4-digit-7-segment-display-working-with-an-arduino/

MichaelG.

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Nearly to years later … rummaging through my electronics scrap-box, I found the two assembled boards and wondered what, if anything, might be worth salvaging.

Curiosity led me to YouTube, where I found two interesting videos

**LINK**

**LINK**

Case closed

MichaelG.

Can’t you redefine the project as write your own clock code? After all you do have the hardware.

regards Martin

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In a word, No

In several words :

1. I have neither the knowledge to write the code, nor the will to learn how
2. The nice man in the first video offers a download of his code, but anyway
3. I couldn’t justify the additional expense of the programming device

I only posted today for the sake of ‘closure’

MichaelG.

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P.S.

The kits are still available, silly-cheap on ebay

… just search for AT89C2051 DIY Electronics Kit

No idea if they are still duff though.

Edited By Michael Gilligan on 25/02/2023 21:36:14

Michael, I could lend you the programming device k assuming it's a Pic) but I'd not know how to use it. Mine came with a load of other stuff, and is too good to throw away

Not really a serious suggestion more sort of tongue in cheek.

regards Martin

If it’s a PicKit programmer you can do in circuit programming and debug with it if you provide the connections on your board. Works with the MPLab development environment freely downloadable from the Microchip Technologies website. Runs on Mac or PC.

regards Martin

Thanks for the thought, Martin, but [so far asI’m aware] it’s not a Pic

… and I really don’t want to try to learn a whole system for the sake of two chips.

I’m struggling enough with the easy stuff.

MichaelG.
 

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Edit: __ for what it’s worth

Edited By Michael Gilligan on 25/02/2023 22:51:59

I did get the message you had given up with the clock. PicKit info posted as a response to Duncan and a general bit of info for anyone who might find it useful.

regards Martin

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Sorry, Duncan … I missed the fact that it was you making the offer

I was too busy trying to respond to Martin

MichaelG.

I've no doubt that the code in Michael's link of 11/05 works, but it is making heavy weather of it. If you drive all 8 segments from one port you can tell it which character to write by putting portA = 0b01010101 or similar instead of the 8 lines for each character. Faster as well, not that it probably matters

Good morning folks …

I now see that I managed, last night, to mess-up the cosmetics of this thread by copying and pasting text from a web-page.

… The old ‘text running under the adverts’ trick.

… Might have been better to not bother

MichaelG.

I found the thread interesting as an example of the need to get everything right!

Someone has designed a circuit, and a pcb, and bought and packaged all the components for a reasonable kit. They wrote a clock program in PIC Assembly language, and tested it on a prototype.

All good until someone made a basic mistake by sending the PIC chip supplier the program's source code rather than the compiled machine instructions. Thus large numbers of PIC chips loaded with duff code and sent out.

A rough rule of thumb in IT Projects, and it's generally true of all new design, it that the cost of fixing a mistake multiplies by 10 at each successive stage. Errors detected on the drawing board are cheap and easy to fix; the same mistake discovered by customers in the final product can cost millions to fix, perhaps more than the product sold for. Product recalls are horrifically expensive, involving substantial organisation, paying transport costs at retail-rates, dealing with items lost or damaged in transit and other complications. Often better to send a replacement, go bankrupt, or hide under the bed.

Dave

Addendum: [might be useful to someone, sometime]

**LINK**

https://github.com/ruthsarian/at89c2051_clock

MichaelG.