If it is always 13.5V, why do you speak of fluctuation?@KlausST : 13.5V. I saw voltages fluctuating. Measured using voltmeter.
Hi,
Please provide more detailedinformations.
If it is always 13.5V, why do you speak of fluctuation?
You don't say what output voltage you expect. You don't say what fluctuations you see.
We can not know this informations..
Klaus
Step-down converter with no feedback to regulate output will follow the peak voltage of an unloaded AC input. Loaded may drop up to 40% to Average after rectification depending on effective RC filter and loading.
Is this the rated voltage or the measured voltage at no load?My Wall wart supplies 16.6VDC.
Is this true for all your given measurement values? Or is there sometimes the battery connected?Fluctuating voltage is measured in no load condition.
I hope you are aware that the LM317 needs about 1.5V voltage drop. So if the input voltage is 12V you maximally (reliably) can expect an output voltage of 10.5V.Wall wart output rating: 12V, 800mA., LM317 output voltage needed: 13.5V, 100mA.
16.6V is an unusual voltage for a wall wart, is that the voltage marked on it or is it what you are measuring with your meter. If it's your meter reading it could well be a nominal 12V adapter but measured under no load, in other words it would be expected to drop to 12V at or near to it's rated current, it may not be proving enough voltage to the regulator while under load. Can you measure the voltages on all three pins of the LM317 and tell us what they are please. Take the measurement with no load and also with the SLA connected.@betwixt : My Wall wart supplies 16.6VDC. I connect it to LM317 and step down to 13.5V.
Hi,
Is this the rated voltage or the measured voltage at no load? (Ans: measured voltage at no load using voltmeter)
Please measure the LM317 input voltage. What range (min ... max) do you see? (Ans: 16.6V, 16.5V )
Is this true for all your given measurement values? Or is there sometimes the battery connected? (ans: no battery is connected)
How reliable are your DVM readings? Are they stable when you measure the voltage of an unloaded battery? (ans: without battery connected, output voltage keeps changing from 13.5V, 13.4V)
I hope you are aware that the LM317 needs about 1.5V voltage drop. So if the input voltage is 12V you maximally (reliably) can expect an output voltage of 10.5V. ( Ans: Will need more time to find out)
Klaus
16.6V is an unusual voltage for a wall wart, is that the voltage marked on it or is it what you are measuring with your meter. If it's your meter reading it could well be a nominal 12V adapter but measured under no load, in other words it would be expected to drop to 12V at or near to it's rated current, it may not be proving enough voltage to the regulator while under load. Can you measure the voltages on all three pins of the LM317 and tell us what they are please. Take the measurement with no load and also with the SLA connected.
Brian.
Planning to connect the wall wart to a 16V zener diode which will give constant 16V and then transport to the LM317 circuit and step down to 13.5V.
Wall Wart(16.6V) >>> 16V zener >>> LM317 >> down to 13.5V
Here I ask to measure the battery voltage. But your answer sas without battery....How reliable are your DVM readings? Are they stable when you measure the voltage of an unloaded battery? (ans: without battery connected, output voltage keeps changing from 13.5V, 13.4V)
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