All Questions
Tagged with lm78xx power-supply
12
questions
0
votes
2
answers
84
views
Dual power supply, AC to ±12V DC, based on LM7812 + LM7912
I'd like to build a power supply, based on the LM7812 and LM7912, that outputs both +12 V and -12 V. I found this circuit online:
According to the datasheets, the LM7812 has a typical dropout voltage ...
- 113
1
vote
1
answer
227
views
Make a switchable steady 5 V output circuit
I am looking to make a very accurate steady 5V power supply that can be switched on and off using the digital IO pins on an Arduino. I planned to use a 9V power supply connected to a 2N2222 transistor ...
- 13
3
votes
1
answer
110
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What could have caused my power supply to fail?
I made a dual +/- 12 V power supply for synthesizer circuits using a schematic by Moritz Klein (image below). The input of the supply is from a 12 VAC transformer.
After soldering the circuit on a ...
- 33
0
votes
2
answers
347
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LM7805 decoupling capacitors
Would it be possible to replace these combinations of ceramic and electrolytic capacitors with just a pair of low-ESR 10 μF ceramics?
Conversion from 12 V to 5 V, minimal consumption, only MAX485 ...
- 15
0
votes
2
answers
178
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A question about 78XX power supply design
I want to get 12V and 5V from a 24V power source. 12V drives a MOSFET H bridge and a cooling fan. 5V is for a microcontroller. I have already damaged a microcontroller due to a failed 7805 regulator.
...
- 103
1
vote
2
answers
2k
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LM7805CV output voltage drop to 2.5v after connecting load
I've made a simple linear power supply for micro-controller with a transformer and LM7805CV as seen in the picture.
LM7805CV input voltage is 35V and output without load is 5V but after connecting a ...
- 55
0
votes
2
answers
273
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Decoding power supply regulation (42V from 5V)
I am referring below schematic where 42V is generated from LM78L05 regulator IC. But I am not able to get how LM78L05 can generate 42V? Which concept is used to get such high voltage from 5V regulator ...
- 739
-1
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2
answers
338
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xV input from a wall wart to +9v, -9v, +9v output
I am trying to modify a circuit Circuit schematic that requires three 9v batteries. Two to supply +9v/-9v for an lm358N opamp, the other +9v is to drive a DMM display.
I have dozens of wall warts of ...
- 111
4
votes
4
answers
2k
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Switch Mode Alternative to LM7805/LM7905
I am attempting to design a dual rail power supply PCB for a university project. There are a number of restrictions - namely that it maintains > 80% efficiency regardless of the current draw. I was ...
- 165
0
votes
3
answers
2k
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LM7915 delivering more than -15v
I'm trying to build a regulated power adapter using LM7915.
Before everything, I built on a protoboard the schema included on the datasheet (from ST). But, instead -15v, the output is -19v...
I'm ...
- 175
0
votes
3
answers
2k
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48V DC Power Supply Using LM7812 in Series
I want to create a 600W 48 VDC power supply with input taken from the line (220VAC) and so far the steps that I've had in my mind are:
Stepping-down the voltage to 15V using transformer with 3A ...
8
votes
3
answers
2k
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Can I obtain a new voltage source from outputs of two cascaded linear voltage regulators in practice?
I have a device which works with 7V. I have a 7812 and 7805 already running in the circuit. Can I use the outputs of this voltage regulators to feed the 7V device?
I know this is possible in theory. ...
- 14.1k