DIY Adjustable Constant Load (Current & Power)
video description
I accidentally fried my LTC3780, and I did a lot of probing and I noticed that the under voltage regulation caused some problems when set to 0.
The fried LTC3780 could only tune from 0. 8v to 2. 5v (fault light on above that) and had no current limiting.
So here's what I learned:
If you set the under-voltage pot to as low as it goes, then the full supply voltage will pass to the LM358 to an opamp input while the supply voltage is at a regulated 5v. Even though it's supposed to only produce 5v out, it started to fail for me and will go up to near the supply voltage which feeds the run pin of the LTC3780. The LM358 still worked if the trimmer was set closer to the supply voltage though, so clearly it puts more stress on the LM358 to pass much higher voltages to the inputs than the 5v regulated voltage. If the undervoltage pot is tuned closer to the supply voltage this creates a voltage divider that will make the input voltage to the LM358 closer to the regulated voltage.
Any voltage above about 6v to the LTC3780 on the run pin will destroy it.
So, my advice is turn the undervoltage regulator all the way up, so that you get the fault light and the output goes to 0, and then turn it down until the fault light turns off, and overshoot a little (but don't set it to the minimum. As long as you're using a constant supply voltage it'll continue to run, and this will reduce risk of frying the LM358 which will fry the LTC3780 (The IC is same cost as the whole board really, so you don't want to have to replace it.
Date: 2020-09-05
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Comments and reviews: 9
Marinus
Great info. I've been looking for a PSU that can output 0. 70. 9 Volts and 'push' out a constant current at 0. 5 Amps and up (both adjustable) for electroforming/copper plating small hobby projects. Sadly the Lab PSU's I've bought do not work well for me so I would have to start making my own. Do you think it's even possible for a PSU to 'push' out constant current at such a low voltage? Apparently most Lab PSU's are not able to do this.
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Great info. I've been looking for a PSU that can output 0. 70. 9 Volts and 'push' out a constant current at 0. 5 Amps and up (both adjustable) for electroforming/copper plating small hobby projects. Sadly the Lab PSU's I've bought do not work well for me so I would have to start making my own. Do you think it's even possible for a PSU to 'push' out constant current at such a low voltage? Apparently most Lab PSU's are not able to do this.
reply
Ed
Hey guys! I need to inject amperage from 10mA to 10mA increments at cellphones lines when they are shortcut-ed. That's what I do to find between dozen of suspects components that always is one generally a Cap that has the short cut to GND.
But my power supply is really annoying to limit the current even with the fine adjuster. If I build this I will be able to get small load from 10mA, to 20mA, to 30mA depending on what I need mA I need.
reply
Hey guys! I need to inject amperage from 10mA to 10mA increments at cellphones lines when they are shortcut-ed. That's what I do to find between dozen of suspects components that always is one generally a Cap that has the short cut to GND.
But my power supply is really annoying to limit the current even with the fine adjuster. If I build this I will be able to get small load from 10mA, to 20mA, to 30mA depending on what I need mA I need.
reply
Mojo
Always wondered why you cannot buy cheap electronic-loads with a CP feature. You're talking about 100's of for something with CP. As this video shows, it's not that difficult to achieve, and most cheap electronic-loads will already have an MCU - a bit more circuitry, a sprinkle of code and bob's your uncle! Surely some chip maker has already produced an MCU with higher than 8-bit resolutions for precisely jobs like this?
reply
Always wondered why you cannot buy cheap electronic-loads with a CP feature. You're talking about 100's of for something with CP. As this video shows, it's not that difficult to achieve, and most cheap electronic-loads will already have an MCU - a bit more circuitry, a sprinkle of code and bob's your uncle! Surely some chip maker has already produced an MCU with higher than 8-bit resolutions for precisely jobs like this?
reply
Dinozor
Hello Big Scott. This is a wonderful project that I want to assembly. However it has some particularities as described in the audio of the video. I noticed that there is English subtitles. My question is if you have a manual of this project, or if you have the text spoken in the video. I need to translate to Portuguese for the correct understanding of the operation. Thank you for your attention
reply
Hello Big Scott. This is a wonderful project that I want to assembly. However it has some particularities as described in the audio of the video. I noticed that there is English subtitles. My question is if you have a manual of this project, or if you have the text spoken in the video. I need to translate to Portuguese for the correct understanding of the operation. Thank you for your attention
reply
education
Interresting project! It's always usefull to have a load that can be ajustable. Could be programmable too. I was wondering if you know some PSU like your DPS5315 which is programmable and not too expensive. The problem with the DPS 5315 is that everything is in German. Not sure if it can communicate with SCPI protocole as well.
Thanks
reply
Interresting project! It's always usefull to have a load that can be ajustable. Could be programmable too. I was wondering if you know some PSU like your DPS5315 which is programmable and not too expensive. The problem with the DPS 5315 is that everything is in German. Not sure if it can communicate with SCPI protocole as well.
Thanks
reply
mali
Thanks for this Project.
With it I learned how to build Menu for LCD screen.
I didn't have a 16x2 LCD, but I did have a few Nokia 5110 LCDs, so I decided to adjust the code for that LCD.
And guess what. It works: )
reply
Thanks for this Project.
With it I learned how to build Menu for LCD screen.
I didn't have a 16x2 LCD, but I did have a few Nokia 5110 LCDs, so I decided to adjust the code for that LCD.
And guess what. It works: )
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SpudHead
You can use a differential amplifier to not only drop the hall sensor output voltage at 0A to 0V but also amplify the output at max current to 5V giving you as much resolution as possible for the current sensing.
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You can use a differential amplifier to not only drop the hall sensor output voltage at 0A to 0V but also amplify the output at max current to 5V giving you as much resolution as possible for the current sensing.
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Priyabrata
You can use use STM32 in place of atmega328 for better ADC and PWM resolution. Or INA219 with a lower value shunt resistance can offer you higher current range and stable power measurement.
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You can use use STM32 in place of atmega328 for better ADC and PWM resolution. Or INA219 with a lower value shunt resistance can offer you higher current range and stable power measurement.
reply
Frank
Thanks for the code on instructables I'm working on a lab power supply and I'm reverse engineering your code to build my menu without your code I'd be so lost thank you
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Thanks for the code on instructables I'm working on a lab power supply and I'm reverse engineering your code to build my menu without your code I'd be so lost thank you
reply
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