An electronic device which supplies electrical energy to a load. Can be AC or DC input. Typically DC output.
39
votes
3answers
18k views
Choosing power supply, how to get the voltage and current ratings?
Power supplies are available in a wide range of voltage and current ratings. If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to ...
37
votes
5answers
5k views
My linear voltage regulator is overheating very fast
I'm using a 5V/2A voltage regulator (L78S05) without a heatsink. I'm testing the circuit with a microcontroller (PIC18FXXXX), a few LEDs and a 1mA piezzo buzzer. The input voltage is ~24V DC. After ...
9
votes
2answers
2k views
How do I select the accompanying components for an optocoupler?
I'm using an optocoupler (MOC3021) to sense the On/Off state of an electrial appliance using a microcontroller ATmega16L. How do i go about doing this? My mains supply specs are 230V, 50Hz. How do I ...
19
votes
6answers
3k views
How to convert AC to DC
I am designing a circuit that needs to output 5VDC @ 1A. I'm trying to use a wall transformer to step the voltage down to 12VAC. The next step is the diode bridge and ripple capacitor.
The ripple ...
16
votes
1answer
3k views
How can I detect a power outage with a microcontroller?
I have the following power supply configuration:
AC MAINS -> UPS -> 24V POWER SUPPLY -> 5V VOLTAGE REGULATOR -> PCB (microcontroller).
What's the best solution to detect the power outage on the mains ...
17
votes
4answers
4k views
Switch between 5V power supplies?
I'm designing a board that can be powered either by USB or an ATX power supply. They can both be plugged in at the same time, independently. I'd like the ATX to provide 5V if its plugged in, but ...
7
votes
3answers
2k views
How to discharge smoothing capacitors?
I have a simple 12V 10 A power supply with just a transformer and a rectifier. After doing some research and simulations, I've added 3 10 mF capacitors in parallel to smooth out the output.
My ...
6
votes
4answers
1k views
Shutdown Controller for Raspberry Pi in a car
Following on from my previous question I'm trying to create a shutdown controller for my Raspberry Pi. The Raspberry Pi needs to be powered from the battery, but should power-down after the Pi ...
4
votes
3answers
258 views
How would you detect vampire/standby power?
Is it possible to detect when a device is consuming power in a stand-by or nominally off state? For example if I leave my charger plugged in, detect that a small amount of current is being drawn and ...
2
votes
4answers
452 views
Limiting current from a 5v power supply [duplicate]
Possible Duplicate:
Choosing power supply, how to get the voltage and current ratings?
I have a 5V / 1A regulated supply. I'm thinking of using it to power a PCB which asks for 5V and ...
5
votes
3answers
827 views
Using multiple power supplies to increase current
I need 1300mA at 3.5V, but the highest power AC-DC wall adaptor I have is 1A 12V. Is it possible to use two of these to get ~2A? I'm thinking that diodes would be needed from the positive pins of the ...
5
votes
3answers
541 views
Best way to produce 50 VDC, 20 mA from 5 V
Ok, so I need to generate 50 V from 5 V, with a load of 0 to 20 mA, for a mass-produced device. There are simple boost converter circuits like this LT3467 example:
but it seems these are limited ...
8
votes
2answers
798 views
Is it normal for DC wall adapter power supplies to provide voltages above the nominal ones?
When I measure a 9V DC wall adapter power supply with a multimeter it shows 11.8V. When connected to my board this voltage lowers to 10V. Is this normal? Should I be afraid of toasting my 1117CD-5.0 ...
5
votes
1answer
242 views
'Voltage Fuse' or better
I have a power supply with multiple outputs (5v, 12, 24v)
According to the manufacture (and after testing) there must be a minimum load on the PSU for it to supply the stated voltages. Without a ...
9
votes
3answers
2k views
How to implement a soft power switch controllable by microcontroller?
I want to design a circuit such that the microcontroller can toggle a GPIO pin and shut the whole system (including microcontroller itself) down. And when the user presses a momentary button, the ...
10
votes
4answers
583 views
What are some alternative power sources for wireless sensors?
I'm looking to power several small, Wi-Fi enabled sensors, in a domestic home or office environment. As such I'm interested in keeping them powered as long as possible between charges.
Obviously an ...
7
votes
5answers
3k views
How efficient is a capacitive power supply?
Something like this
Falstad sim version of it
(I'm tired, I keep making mistakes, so please excuse me for the second time.)
Now these are not very safe PSU's, due to the lack of isolation. But in ...
8
votes
4answers
791 views
What are the basics of making a rechargeable battery pack?
We have a device that runs off of a AC adapter, or a pack of 8 AA batteries. Since in normal use we use both, it would seem to make sense to have the battery pack recharge while using the AC adapter - ...
15
votes
5answers
725 views
Why is it so problematic to have close to zero standby power consumption?
Each electronic device consumes electric power when it is "idle" unless it has a mechanical switch. I can understand that for example a TV with a remote control needs to "be ready" to receive a ...
11
votes
4answers
4k views
What is “foldback short circuit protection” in a power supply?
I am looking at buying a 24V power supply. Two of the options are these:
PSP24-060S 24 VDC 2.5A (60W) power supply
PSB24-060-P 24 VDC 2.5A (60W) power supply
The first offers "foldback short ...
10
votes
3answers
502 views
Simple \$12V_{AC}\$ to \$12V_{DC}\$ Rectifier
I want to convert a \$12V_{AC}\$ power supply output to use \$12V_{DC}\$ to power some outdoor LEDs.
The power supply as it stands will light the LEDs (with a slight flicker from the reverse ...
7
votes
1answer
278 views
Why does short distance wireless energy transfer have such low efficiency?
Wikipedia and numerous other sources cite the following statement about Magne Charge high-power inductive charging system:
For example, the Magne Charge system employed high-frequency induction to ...
5
votes
2answers
2k views
Arduino backup power supply
As a complete beginner in the field of electrical engineering, I am trying to build an alarm system on an Arduino board. I want to power my board using an external 10V power supply. In case of power ...
3
votes
4answers
334 views
Delayed power supply startup
I would like to make a circuit that turns on a power supply to a microcontroller after holding down a button for a period of time (say 2 seconds). To make matters slightly more complicated, if ...
2
votes
3answers
262 views
Charging 3 AAs in series
I'm currently repairing a project built by someone else and want to avoid tinkering with it as much as possible.
I am looking to recharge 3 AA NiMH batteries (at 1.2v each), that are in series.
I ...
6
votes
2answers
816 views
Ripple current in a linear power supply transformer
I'm a bit confused regarding linear supplies and their input currents (i.e. on the input side of the voltage regulator).
To start with, here's a test circuit:
\$R_{bogus}\$ is just to make LTspice ...
3
votes
2answers
201 views
Heat Generation Question
Sorry for my previous vague question. I am setting up a heat generator map for my thermal analysis and I was given that one of the ICs will be dissapating 5.2W. Does this mean that 5.2W of heat will ...
2
votes
3answers
922 views
Measuring voltage/current digitally on two separate power supply rails
I'm designing a dual-rail DC power supply, with the two rails completely separate (except for sharing a dual-secondary transformer). The main design should work as-is, only by adding a fuse + mains ...
0
votes
4answers
534 views
Powering a breadboard with USB
I've recently become quite interested in building small breadboard computers. I've been reading a site that seems to be aimed for beginners, that builds a simple breadboard computer using the 6502 and ...
5
votes
3answers
1k views
Help needed optimising simple current limiting circuit
I have been experimenting with simulating current limiting circuits. I am trying to limit current to ~500mA given a fixed 4.8V source. I have started using a circuit like the one found on this ...
3
votes
1answer
582 views
What component of my phone charger produces chirps and how does it do that?
My Nokia cell phone is charged with a very lightweight compact charger similar to this AC-15 (can't find the one I actually use).
While the battery is close to empty the charger works silently - just ...
2
votes
2answers
236 views
Can this temperature-controlled fan circuit be modified for different input voltage?
I want to know if this same circuit can be used for 220 or 230 volt input, and if there are any components that need to be modified. C3 has 600V capacity and C1 and C2 have 250 volt.
Link to ...
2
votes
2answers
374 views
Will a 5.1V adapter charge a device that currently uses a 5.5V adapter [duplicate]
Possible Duplicate:
Choosing power supply, how to get the voltage and current ratings?
I have a device (a Geneva XS portable Bluetooth speaker) which is supplied with a power adapter that ...
1
vote
2answers
125 views
How do I determine the maximum amp output of a battery pack?
How can I determine the maximum amp output of a battery pack?
Some background: I've got a 5-AA battery pack hooked up to a microcontroller and some continuous rotation servos, but there's current ...
1
vote
2answers
253 views
Transformless power supply without ground
I would like to make a transformerless power supply, I found some description on the Internet like this pdf provided by Microchip. My question is it is possible to use only the phase line(without ...
1
vote
3answers
2k views
Which electric components could make a high pitch sound when defected?
My PC's ATX power supply stopped working. I opened it and noticed that it makes a high pitch sound when turned on. I can't figure out which component in the power supply makes that sound, so that I ...
0
votes
5answers
773 views
Supply power to mini-ITX from car battery
Two related questions have been combined here as the answers and concepts overlap:
(Q1) We are building a robot that will be controlled by mini-ITX PC. The power source for robot will be detached ...
19
votes
3answers
3k views
Can I replace all electrolytic capacitors with ceramic ones?
I am designing the power supply circuit for a system that needs several supplies, my questions are:
Is it possible to replace all electrolytic caps (Mostly 100uF) by ceramic ones? What are the ...
9
votes
5answers
2k views
24VAC/5VDC power supply design
I am planning to create a water valve controller using an MCU and a set of solenoid-controlled valves. The solenoids run on 24VAC (40mA inrush, 20mA holding).
The MCU is on a board that draws ~100mA, ...
18
votes
4answers
2k views
When a battery is your power source, what is ground?
For the sake of not incorrectly connecting my power supply and damaging my board I'm going to ask a relatively dumb question. Is ground on my board the negative terminal on my battery? Explicitly ...
12
votes
4answers
740 views
Considerations in a bench/lab power supply?
I'm looking at adding a low-cost variable power supply to my electronics hobby bench. After years of cobbling together LM317's and LM7805's, it's about time...
Considerations:
I've found a few ...
6
votes
4answers
1k views
Least expensive way to plug in a microcontroller into 120V (without wall wart or batteries)
I need to be able to power a Atmega168 by plugging it into a wall. The circuit is a little bit more complex but not too much. The Atmega168 needs between 1.8V and 5V at 200mA. The ideal solution ...
6
votes
4answers
667 views
How does a wireless charger work without a magnetic core passing through both “coils”?
Every time I hear the description of a wireless charging system it goes like this: "remember a transformer? It's the same here - one coil is in the base and another is in the device and when you put ...
16
votes
4answers
4k views
What's the purpose of two capacitors in parallel?
What's the purpose of the two capacitors in parallel on each side of the regulator in
this power supply circuit
I've seen similar setups in other similar circuits and can guess that it's related ...
9
votes
7answers
5k views
How do I convert 9 V DC to 5 V?
What's a good way to reduce the output from a 9V battery to the 1.8V to 5V required by an ATmega328 controller? The context is a small robotics platform with low power requirements (very slow ...
7
votes
2answers
351 views
Does switched-mode power supply feature galvanic separation?
I've carefully read Wikipedia article and can't get one important thing - is there galvanic separation in such supply?
The diagram in that article goes like this:
...
7
votes
4answers
839 views
Different ways to digitally control an adjustable SMPS
I want to make a battery powered, adjustable SMPS for use in situations when I cannot have an outlet near me, so I would like some more information or suggestions about this topic. The SMPS chip I am ...
6
votes
7answers
580 views
Simplest Way to step down the 220AC with more than 10% efficiency
Objective
I want to design a tiny single packaged mains-powered temperature sensor. Possibly as a multi-chip module (MCM) on one small PCB board.
Constraints
The temperature sensor I plan to ...
6
votes
4answers
725 views
Benchtop power supplies: linear vs switching?
I'm looking into getting a decent benchtop power supply ($150-300) for hobby-level electronic design and testing. I don't want to modify or use a computer ATX supply because I want:
Adjustable ...
3
votes
5answers
2k views
Ultra low noise power supply
I am trying to design an ultra low noise power supply for my sensitive circuit. The supply will provide 5V and 600mA. (Worst case, 200mA typical). My input voltage is 2V to 4V. My ripple target under ...
