16 thoughts on “Voltlog #39 – 60W Dummy Load Reverse Engineering”

  1. Hello,
    I have disassembled and photographed the display board to do so.
    The data transmission to the display is via SPI bus. The display 2 piece TM1650 are used as drivers.
    If you (also translucent via Photoshop) would like the photos, send an email to: [email protected]


  2. I understood already in the presentation of the video, but no idea where can I find your “video descriptions”

  3. Could you find where does pin 26 of the chip connects?. It would be the more reasonable choice pin if the free ports L and/or F are for SWIN (DATA) connexion with a ST-Link programmer. However, as far as I found from your excellent work, L seems to be connected to pin 32 (TIM1_CH4 [AFR4]) and F to pin 27 (TIM1_CH3 [AFR3]).

  4. Thanks for your prompt reply. I couldn’t see the programming header. Pin 1 seems connected as well to Pin 32, isn’t it?. Then this ‘L’ would be the NRESET pin. If so it would make sense that a SWIM connector from a ST-LINK/V2 programmer (20 EUR) can be connected to the programming header you mentioned and the Reset pin to L (Vc and G are obvious). It would be great to fully reverse engineer the electronic load making open source code for it… maybe can be made to work by software in Constant Voltage or Constant Resistance mode. Of course all this would require knowledge of the STM-Studio or IAR programming environments.

  5. My ZPB30A1 is off in current ratring by about 100mA. If I set the load to sink 1A it really draws 900mA. Is there a way to adjust this deviation?

    Perhaps by twiddling with R37 in your schematic (MOS-FET Gate resistor)?

    1. Changing the value of R37 will not affect the current. First, you have to know whether your error is a gain (proportional) or offset error: the one example you gave does not show either, you need (at least) 2 points to determine which it is. In other words if you set it to sink 2 A and it really draws 1.8 A then you have a gain error. Considering that this is in fact the most likely failure then I’d look at the voltage divider R16 and R17: if you want to increase the current then you need less division: making R16 smaller would do that.
      Another aspect is how do you know that your measurement of the current is better than what the device says? Are you using something that has been recently calibrated?

  6. Thanks for the reverse engineering! A lot easier with caps when the values are marked on the PCB eh? I just received the 110 W version of this only to find that the thermistor was broken ( “Ert” error right away as soon as the On/Off button is pushed). I’m an EE design engineer so no real problem. I used an R substitution box and found that the lower the R the faster the fan, so an NTC thermistor would be needed. I also found that at R values less than 19 K the fan runs even when the device is not in run mode, presumably to cool it down after a hot run. Under 5 k causes the “otp” condition, and something like greater than 860 k causes the “Ert”. Presumably the firmware is different, but has anybody looked at the 110 W version for potential component value changes?

    1. To partially answer my own question, the FET is different in the 110 W version: it is a IRFP260N not a W60N10. This looks like it can handle higher power, 300 W at 25C vs 200 at the same temperature. And as is obvious from the photos on Banggood the heat sink is larger.
      Love the marketing talk “110W: the shell will be upgraded to silver color !” when the black version would be a better heat sink than the silver (and yes mine is bare Aluminum).

    2. Although I have the 110W version I haven’t spent too much time on it, especially on the component level changes. I tend to use the 60W version most often because it covers my needs so the 110W mostly sits in a box. The firmware is certainly different though.

      I noticed the Chinese suppliers tend to say “upgraded” whenever something is different/changed.

  7. Hi Voltlog,
    Hope you don’t mind sending you a mail. Did you know, there’s two versions of this 60w load. The one with the red tactile switch and the one i got with the black tactile switch.My one got a 15mm fan and the red one got a 20mm fan
    Maybe you can help me finding the error codes for this load tester, please.

    1. The seller should provide info on the product he sold you. I don’t have any other info, just what I published.

  8. Hi! I think I’ve found a little mistake. The PWM FAN DRIVE should have a capacitor connected to fan-inductor net (FAN- pin). Because it’s just a buck converter (open loop) it requires a capacitor at the output.

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