VOGONS


Fabricating a New Turbo Display

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Reply 60 of 75, by HanJammer

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Socket3 wrote on 2020-12-03, 15:13:

I'd be interested in purchasing several (4-5 units), but with a 3 digit display... I have several pentium 233 and k6-II/III PCs in AT cases with missing MHz displays....

^this

and what we really need are those (attachments) as they are very rare and everything else is relatively easily sourced from cases that are going to trash.

Good job on the display anyway.

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Reply 61 of 75, by appiah4

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@wiretap I will be building five of these for my cases, I just wanted to confirm that the following code, schematic and boms are final:

Code: Re: Fabricating a New Turbo Display (Also, is this simulation only code or do I flash this onto the PIC16F690 controller directly? Or is there another code for the real chip?)
BOM: Re: Fabricating a New Turbo Display
Schematic: Re: Fabricating a New Turbo Display

Could you confirm? Or post if there are newer?

I also had a few questions I hoped you could answer..

-Would using 150R resistors in place of 145R ones be an issue?
-Would using 3.9KR resistors in place of the 3.8KR ones be an issue?
-Does the circuit really need a low noise transistor? I have BC548, would it be an issue?
-What voltage rating is the 10uF electrolytic cap? The 10uF ones I have are significantly larger, would a 10uF 25V tantalum work in its place?

And finally, a bonus question:

-Does the code only interprete numerals for the display or can it also interprete alphabetical characters? ie. can I program it to display HI and LO?

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Reply 62 of 75, by wiretap

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- The 150R resistors would be fine.
- 3.8KR resistors are fine.
- You don't need a low noise transistor.
- A cap of 25V would work fine. Anything 5V or higher.
- The code is 99% there. It made need a little tweaking.
- I didn't include any code for HI/LO, but it could be modified for that if you choose to go that route.

I don't have any further updates on the project since I've been far too busy with work, family, and home schooling 2 of my wife's nephews.

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Reply 63 of 75, by wiretap

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A little better 2-digit design.. easier to implement and program. Less complicated as well. Based on an ATTiny85, so Arduino guys should be able to build and program this easily with minimal cost.

Still needs code. Basically the code would be:
- read the state of PB0 to see if the PC's turbo LED is on (TLED of motherboard hooks up to this)
--- If PB0 is high, turn on PB2 (TLED_OUT) to turn on the turbo LED.. and output serial data on PB3 (clock is PB4, latch is PB1) for the turbo MHz to display.
--- If PB0 is low, turn off PB2 (TLED_OUT) to turn off the turbo LED.. and output serial data on PB3 (clock is PB4, latch is PB1) for the normal MHz to display.
- go back to reading PB0 again

This design can be cascaded to as many digits as you want, just by tapping into the 74HC595 serial output, and of course modifying the serial output code for as many digits as you need.

Pics, BOM, KiCAD project attached. I autorouted it because there's a lot of small traces that need tons of vias, so feel free to try to do a better job 🤣. Also, I think I left enough room in all 4 corners to move the cutouts for mounting if you need to. In KiCAD, you can just select the edge cut layer and move the holes as you need them.

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Reply 64 of 75, by adalbert

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Hmm, are two 74HC chips necessary here? Couldn't it be simplified further by connecting the displays in parallel (except common pin for power) and switching the power rapidly between digits (200Hz or faster)? That's display multiplexing 😀 /edit: seems that you even used multiplexing in earlier simulation/

Repair videos: https://youtu.be/T6mXM1tA7pA

Reply 65 of 75, by wiretap

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That could have been done, but you'd need more than an ATTiny85 to do it for enough I/O pins. And yes, two 595's are necessary here.

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Reply 66 of 75, by adalbert

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Sure, there are not enough pins so sorry. I even used two 74HC with ATTiny by myself earlier 😁 except I connected 3 digits in parallel to one 74HC, and used another 74HC + transistors for multiplexing.

Repair videos: https://youtu.be/T6mXM1tA7pA

Reply 67 of 75, by adalbert

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BTW speaking of these displays with "MHz" letters:

HanJammer wrote on 2020-12-04, 11:28:
^this and what we really need are those (attachments) as they are very rare and everything else is relatively easily sourced fro […]
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Socket3 wrote on 2020-12-03, 15:13:

I'd be interested in purchasing several (4-5 units), but with a 3 digit display... I have several pentium 233 and k6-II/III PCs in AT cases with missing MHz displays....

^this
and what we really need are those (attachments) as they are very rare and everything else is relatively easily sourced from cases that are going to trash.

Good job on the display anyway.

This can be made, I did something similar (custom display) for flight simulator indicator lights. Level of complexity can vary - it depends if you want to just have all MHz letters light up at once, or do you need to have ability to light up particular segments? (is there any reason for this?)

A mask for the letters needs to be created. It can be a thin PCB with holes passing the light etched in copper. To get rid of copper color, it can be covered with theatrical ND gel adhered to it, or covered with black silkscreen.
Another way for making mask is to use laser-engraved piece of black-on-white ABS board.
OR (home-made version) it could be laser-printer with deep black (mixture of all colors + black on color printer) on tracing paper, then covered with clear tape.

Below that mask will be second PCB with small SMD LEDs of chosen color (or RGB... 😁 😁).
If we want to be able to light up particlar segments: the LEDs need to be precisely positioned in order to match the light mask. Then the LEDs will need to be separated from each other to prevent the light spill - a 3D printed "skeleton" with thin walls can be used for that.
If we just want to light up all MHz letters at once - one LED for each letter could probably suffice, a diffusing material (e.g. diffusion theatrical gel, or tracing paper) could be added to spread the light evenly.
In both cases, obviously a connector needs to be added.

Outer rectangular shell can be 3D printed. LED piece will be on the bottom, mask on the top and there can be hot glue or clear epoxy injected between them.

I would prefer to just make the "MHz" part and join it with already available digit displays. To make the seam invisible, you can just cover both pieces with ND gel, the display will appear to be almost black after that, but as soon as you turn it on, the letters and digits will appear (resistors need to be chosen properly so there will be enough power to make up for the light loss). OR an additional mask to cover the entire piece could be made.

OR it could be possible just to find alphanumeric LED displays, and use these. An additional mask could be printed to cover unwanted segments, or to make the seam invisible.

Repair videos: https://youtu.be/T6mXM1tA7pA

Reply 69 of 75, by SETBLASTER

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HanJammer wrote on 2020-12-04, 11:28:
^this […]
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Socket3 wrote on 2020-12-03, 15:13:

I'd be interested in purchasing several (4-5 units), but with a 3 digit display... I have several pentium 233 and k6-II/III PCs in AT cases with missing MHz displays....

^this

and what we really need are those (attachments) as they are very rare and everything else is relatively easily sourced from cases that are going to trash.

Good job on the display anyway.

hi , where did you buy those leds with the red MHZ ? i have been looking for one of those for a long long time

Reply 70 of 75, by wiretap

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Those have been out of production for the better part of 2 decades as far as I know. An alternative would be to use an alphanumeric style segmented display.

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Reply 71 of 75, by wiretap

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Assembled a board and got around to working on the code.. the numeric display works great with all digits (single and double digit). I just have to test the turbo LED and speed switch sensing.

Code attached.

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Reply 73 of 75, by wiretap

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Let me know some dimensions for a 3-digit. PCB size, digit size, and mounting hole locations. I only have one 3-digit to compare to, and it is in a weird case with other things like hdd/pwr LEDs integrated.

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Reply 74 of 75, by wiretap

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Ok, fully tested the this turbo display. It works great with MHz switching and turbo LED support!

Video:
https://youtu.be/Jka8PfParP4

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Reply 75 of 75, by FAMICOMASTER

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As the original case for my Turbo AT had a two digit unit which decided to let out the magic smoke, I would love to have one of these to replace it with. Would be nice to have a case that fits properly as opposed to the IBM 5170 case I've been using which doesn't seem to fit everything very well.