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TIL Christmas...

A project log for Discrete YASEP

a 16-bits YASEP computer (mostly) made of DIP/SOIC chips like in the 70s and 80s... with 2010's twists!

Yann Guidon / YGDES 10/30/2015 at 00:3611 Comments

Today is display day ;-)

I received these :

They are going to help a lot for the early design of the system. I started playing with them and I was not disappointed:

I'm concerned however about the power consumption. The datasheet is clear that this is not a low-power device.

Displaying "0" draws 0.5W!

Touching the package, I feel it's pretty warm. To me, a warm circuit is not a good circuit but that's the price of vintage here.

Fortunately, undervolting works. The display is "more or less stable" at 3.3V but for safety, 3.5V is a good compromise.

That's about 0.2W, which is "OK". A 4-digit display (16 bits) will draw about or less than 1 Watt, depending on the value.

But where do I find 3.5V switching regulators ? How do I modify one (like a cheap fixed-voltage device) to "offset" the voltage by 0.2V ? Any idea ?

There is also the parallel method of "blanking", but I'm not sure it also reduces the drain of the decoding logic.

Discussions

danjovic wrote 10/31/2015 at 15:47 point

You can get 3.5Volts by means of  a MC34063 or another DC-DC converter.

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Yann Guidon / YGDES wrote 10/31/2015 at 16:34 point

I'm lazy so I reused a TI sample of PTV05010W
I know, overkill. But it's easy and tiny, ready made and no need of large caps :-)

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danjovic wrote 10/31/2015 at 16:49 point

Whoa! 8A!! But you're right, the thing is ready and your objective is not a PSU but a retro 16 bit computer. 

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Yann Guidon / YGDES wrote 10/31/2015 at 18:55 point

It's not retro, it's steampunk ;-)

and the "oversized" module has two benefits : I just put 2 large ceramic caps on input and output, no need of extra decoupling since I won't reach 8A, and I can power most of the TIL311 of the system with 1 regulator (that can be turned off).
And I chose it for the very compact size too :-)
I would have spent more time and PCB surface with a MC34063 or LM2575 and my time is getting short...

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alpha_ninja wrote 10/31/2015 at 14:57 point

Heh, looking at that image I first thought you had ordered tons of red boards and forgot to upload your soldermask gerber :P

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Yann Guidon / YGDES wrote 10/31/2015 at 16:36 point

Hahahaha :-)

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danjovic wrote 10/31/2015 at 09:19 point

Same for me! I have 6 of them lying around waiting for the day they'll become a clock.

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Yann Guidon / YGDES wrote 10/31/2015 at 13:38 point

What are you waiting for ? others have done it and it's quite easy with these parts :-)
Good luck !

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danjovic wrote 10/31/2015 at 15:20 point

I have some stuff to finish first. But either way thank you for the incentive! At lease at took them from the drawer to take a look. I was wrong about the amount of pieces. I have 6 units of HP5082-7300 and 3 units of TIL311 (from Texas).

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esot.eric wrote 10/31/2015 at 03:47 point

Whoa, you got a lot of 'em! I've four in my supply, I keep 'em round like gold, they're so easy to throw on a bus. Good luck with the power-consumption issue!

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Yann Guidon / YGDES wrote 10/31/2015 at 04:07 point

They should not be thrown /under/ a bus though ;-)

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