I have built this power supply and its only going to 11.6 volts. I have a 24 Volt transformer. I wanted to set it to 16 Volts. I cant see where I have gone wrong
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Bertus, that is an issue only if the supply is unloaded. This one always has a minimum load (LED and battery) in parallel with the feedback sensing resistor.... R1 can be anything up to ~1KHello,
What will be the load of the powersupply?
C2 is rather small and R1 should be 120 Ohms for a LM317.
For a LM117 the 240 Ohms would be OK.
Bertus
The load is 70mA. I have not got C2 connected at the moment. I am not sure if connecting the 2 windings is correct. The model transformer I have is 042-5052.0Hello,
What will be the load of the powersupply?
C2 is rather small and R1 should be 120 Ohms for a LM317.
For a LM117 the 240 Ohms would be OK.
Bertus
I don't have the battery connected at the moment. I was trying to set the output voltage first but it will not go over 11 volts.Wait until the battery is fully charged, and then measure the final voltage. If the battery is initially discharged (or is bad), then the design is current-limited, and the voltage will not come up until the battery stops drawing current. An SLA or flooded-cell 12V battery will never reach 16V.
C1 is in the wrong place. If used at all (not really necessary here), it should be between pin 2 and pin 1.
C1 might be needed for stability only if the charger is operated without the battery. It needs to be moved so that it is directly across the 317's pins 2 and 1.Without C2 this circuit won't work properly.
To properly calculate C2, here is what you need to know:...What should the correct size of capacitor C1 be and how do you calculate it.
The Voltage across C1 is 32.8Volts and the voltage on pin 2 is 16.1 VoltsWithout C1 were you measuring the output voltage with a DMM? If so, it lied as all DMM's do. Without C1, there is full-wave rectified AC going through everything, not DC. This is not a problem if that's what you want and you know how to use it.
With C1 installed, what is the voltage across C1 and what is the voltage on LM317 pin 2?
ak
Me and everybody else screwed this up. As posted in the original schematic, C2 is the (input) filter capacitor, and C1 is the LM317 (output) anti-oscillation capacitor.But C2 is a input bulk capacitor not C1, you have a typo.
To properly calculate C2, here is what you need to know:
The rms voltage of the secondary winding.
The effective winding resistance.
The forward voltage drop of the rectifiers under load
The maximum output voltage out of the 317.
The maximum load current out of the 317 at the highest output voltage (above).
The drop-out voltage of the 317.
Give me all of these, and I will show you how...
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