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makiyang614

Voltage regulator doesn't seem to be working correctly

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I have a very simple lm317 adjustable voltage regulator put together with a voltage display panel to monitor it. I wanted a 1.5v source to use with the flash circuitry from a camera without having to use lots of batteries.

I have the terminals on the camera circuit wired to output and ground of my regulator. When I turn the camera circuit on however, it charges extremely slowly, and the display meter cuts out. If I turn the voltage up, the display comes back on and displays between 0 and 1v. lm317 has a heatsink and doesn't feel hot. Power is fine when connected to leds. I tried adding a resistor in series with the camera circuitry in case I was drawing too much current, but then nothing happens at all.

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Depending on the flash unit, the max current during charge may be quite high, 5A or more, judging by my Vivitar. The LM317 will current limit (the exact value depends on the version and manufacturer of the device), and the supply you are sourcing the LM317 from may also limit current. If the LM317 isn't warming up, it is likely the supply, not hte regulator. Another possibility is that the supply for the lm317 isn't high enough voltage for the regulator to do its job. It is not low drop out, and the max current goes down as the drop across the regulator goes down. Again, the exact voltage depends on the version, but typical is 1A max at 2V (from the onSemi data sheet) and a 2.5 input-to-output for the rater 1.5A output.

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On 6/8/2017 at 11:08 AM, enl said:

Depending on the flash unit, the max current during charge may be quite high, 5A or more, judging by my Vivitar. The LM317 will current limit (the exact value depends on the version and manufacturer of the device), and the supply you are sourcing the LM317 from may also limit current. If the LM317 isn't warming up, it is likely the supply, not hte regulator. Another possibility is that the supply for the lm317 isn't high enough voltage for the regulator to do its job. It is not low drop out, and the max current goes down as the drop across the regulator goes down. Again, the exact voltage depends on the version, but typical is 1A max at 2V (from the onSemi data sheet) and a 2.5 input-to-output for the rater 1.5A output.

Thanks, for sharing this.

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