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Part 1 reverse engineering the interface on the LED display of the Banshee Ultrasonic gas leak detector to make a MacGyver type countdown timer THING (for demonetisation purposes).
This will be a choose your own adventure project, I don't have anything planned, so let me know what you want to see!
Full video with reverse engineering journey:
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#ElectronicsCreators #MacGyver #Project


27 thoughts on “Eevblog 1491 – the macgyver project – part 1”
  1. Avataaar/Circle Created with python_avatars Mortlet says:

    Unfortunately Youtube has gotten past that stage where spelling the word out has any affect: The auto-captioning clearly understood as it didn't have any spaces in between the letters!

  2. Avataaar/Circle Created with python_avatars rahul kushwaha says:

    microcontrollers are easy, do it all analog. Make your own logic using discrete transistors or ICs, just like the old days. Even a generic uC like one on Pi pico or Arduino nano or the stm32f103 bluepills have enough gpios that you can get away with using all the gpios for driving each segments and not using any shift registers at all, or other multiplexing magic. so that's that. Unless youre using a uC to run a program that is used to drive 7segments to consume least possible current for displaying the best lit number in bright sun, using every bit of processing power to multiplex, then that makes sense, otherwise for fun, go all analog.

  3. Avataaar/Circle Created with python_avatars sparkplug1018 says:

    Id just take some ribbon cables off of the LED display segments over to a new driver board. So "technically" the original board was reused, and would allow different types of driver boards, with what ever fun features to be built. Easy.

  4. Avataaar/Circle Created with python_avatars Broken_Yugo says:

    Wipe off the crappy driver chips, solder on ribbon cable and do the seven segment drive in a non hacky way on the board for whatever microcontroller will probably run the thing.

  5. Avataaar/Circle Created with python_avatars Benny says:

    Keeping the brightness constant is an interesting problem for this board. One way is to have the uP work out how many segments are on and adjust the pwm from the CC for the number of segments on at any one time – a look up table or a on the fly counter bit of code. Still no compensation for variation between segments but better than nothing.
    I'd love to see the solution Dave tries (Chances are it will work well)…this is my DYSS (Daves' Youtube Solution Simulator) at work! Its full of RI (Real Intelligence) and other automation stuff. Its great!

  6. Avataaar/Circle Created with python_avatars Richard Appel says:

    I would like to see it done with discreet logic .that would be interesting. Hmm don't you have a classic chip. Maybe make it audibly count down to .

  7. Avataaar/Circle Created with python_avatars 777anarchist says:

    Build a simple Z80/6800/6502 system (CPU, RAM, ROM, IO port). Retrocomputing is quite popular these days.

  8. Avataaar/Circle Created with python_avatars Randy Carter says:

    Conformal coating. Get a UV flash light. I have one from Amazon that has 100 LED's. The coating glows blue. To remove the coating use Toluene available in the paint dept. of your local hardware store.

  9. Avataaar/Circle Created with python_avatars larry785 says:

    Flip-floppy??? I think it's more like a flopity-flip!!!😂😂😂

  10. Avataaar/Circle Created with python_avatars Hola! Exploatores says:

    I guess "(not) a doomsday device project" is out. youtube are so sensetive 🙂

  11. Avataaar/Circle Created with python_avatars larry785 says:

    It would be really interesting to put a large weight mounted on a motor inside so that it could move by itself.

  12. Avataaar/Circle Created with python_avatars Tony Tone says:

    Cry Key ~

  13. Avataaar/Circle Created with python_avatars David Halliday says:

    Either an STM32 (blue pill?) or one of those cheap as chips micros.

    STM could be kind of cool if you made a circuit to program it over the IR? STM32s are good as they are above Arduino with a good dev set that is in C or C++ and the blue or black pill boards are super cheap.

    Discreet would also be interesting.

    I guess whatever you are most interested in would make the most interesting video as your heart will be in the project.

  14. Avataaar/Circle Created with python_avatars Bert Blankenstein says:

    I'd look at bodging a resistor for each digit. I do not know how hard that would be, but that at least solves some of the display issues, and there is no way you'd want to do 40 droppers. The Pi Pico uses a 2040 chip, should be interesting to go that way.

  15. Avataaar/Circle Created with python_avatars HungryHoagie says:

    Dave if this board doesn't have wifi, bluetooth, LoRa, and 8 different wireless protocols, I'm unsubscribing

  16. Avataaar/Circle Created with python_avatars Gino Avanzini says:

    Would love you to try out the PIO on the raspberry pico

  17. Avataaar/Circle Created with python_avatars Joaquin S says:

    Drive it from ~2.3V or as low a voltage as you need to drive them directly, it would probably do the trick considering the voltage drops of the cc transistor and the 40ishΩ would give a healthy 5 or 6mA to each lead and not exceed the maximum current of the shift register. Brightness would likely be enough and it would be as simple as it gets. If you do need higher voltage for some reason pwm the CC so it gets there. You can't get more brightness than that even if you multiplex the driver, as would only be on for so long.

    With pwm it could get a bit brighter unless you are displaying an 8 in one of the digits, but in software limiting the duty cycle for the maximum segments in at the time in a single digit. Unnecessary complexity, and brightness changing depending on the displayed number, not cool.

    In any case, I want it working anyhow!

  18. Avataaar/Circle Created with python_avatars shisir baral says:

    You must do a prank with this one 😂

  19. Avataaar/Circle Created with python_avatars zaqwerty180432 says:

    You could chuck in one or more solenoids for an interesting clicking sound. Maybe make them hit the inside of the enclosure!

  20. Avataaar/Circle Created with python_avatars TV Account says:

    If it is driven by a micro then you can count the number of segments that will be on once you finish shifting all the data in. That number of segments could be used to control PWM on the current control transistor. With 40 segments on = 100% so 40 x 20mA, and 1 segment on being 2.5% or 20mA.

  21. Avataaar/Circle Created with python_avatars AceMasterX says:

    I understand maintaning the original display and PCB as challenge, but i would like to see a nixie tube or another old type of display, like the ones they used in really old james bond movies.

  22. Avataaar/Circle Created with python_avatars Michael Brown says:

    My least favorite video honestly

  23. Avataaar/Circle Created with python_avatars Mark Loit says:

    My guess is that they drive a single segment at a time for each digit in a multiplexed fashion for a 1/8 duty. This would allow for much better control of the current/brightness of the display, while allowing for the maximum possible current to be delivered.

  24. Avataaar/Circle Created with python_avatars Ray Mitchell says:

    As for the direction of this project, you can probably throw it together with a Arduino tiny… that's what I'd do. If you want to show alternative solutions, once you get that working you can go another route knowing you got it with the Arduino…

  25. Avataaar/Circle Created with python_avatars ZeroHarry says:

    Call it Hot Potato, Dave.

  26. Avataaar/Circle Created with python_avatars WacKEDmaN says:

    arduino micro of some form would be easiest…could add the IR sensors, to switch on/off/modes and will allow to run a movement sensor..needs proximity sensor too!… would be cool if ya could put some leds in the knob bits and have it light up when someone is close…and have the timer start etc…(rgb leds for more effects?!)
    its probably both PWMed and multiplexed.. at quite a high current and brightness changes are minimised..could always cut the traces on the shift registers input and break up the cathode to add resistors…and then drive them all with seperate gpios from micro..

  27. Avataaar/Circle Created with python_avatars WizardTim says:

    The re-shot was a good idea, it's much easier to understand whats going on now.
    Some stuff I thought on the second watch through:
    – Q1 that drives the IR LED has to be an n-channel MOSFET, those 100 series and 10k parallel gate resistors are best practice to prevent sharp rise times and it turning on when the gate input is floating, no clue why they could afford resistors there.
    – Looking at pictures and videos of the thing operating, the display is decently bright but not crazy > 15 mA DC average per segment bright, part of their 'sunlight readable' claim may merely be the fact the display is shaded on the bottom of the unit.
    I can also see the brightness doesn't change with different numbers of segments illuminated both across the same digit and the whole display, but I couldn't find much footage.
    – The only way I can think of them achieving this is if they were counting through the segments A to DP and shifting them out no matter what and using that blanking BJT on the main board if it should be shown on that digit, you would get a constant 1/40th duty cycle for each segment, and minimal flicker at 1 – 10 kHz and the BJT with the 10k resistor could be biased for 90 mA for a single segment within pulsed operation limits. Although it's a super weird implementation if the display is driven directly from that Xilinx FPGA we saw in the teardown I can see it being easier to implement this way than the traditional way on an MCU which I think if this is the case you should do your B 0 M 8 project with an FPGA and recreate this rippled one segment at a time driving logic.

    But I could be very wrong, might also be worth checking the ICs and 7-segments actually work, for all we know the reason it ended up in the mailbag for teardown was because the display failed…

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