Tagged Questions

2
votes
4answers
838 views

Circuit to safely power-down Raspberry Pi

I want to use a Raspberry Pi as an XBMC server in the car. The XBMC docs say that you should always use the shutdown command before disconnecting the power. I don't want to have to (tell my wife to) ...
3
votes
1answer
216 views

What is the capacity of capacitors in this power supply circuit?

Imagine the following circuit with two capacitors and diodes acting as passive PFC. My question is what is the capacity of these two capacitors? I mean compared to a circuit with just a single ...
6
votes
7answers
592 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 ...
7
votes
2answers
265 views

How to buffer an ATMEGA for millisecond-level power interruption without strange behavior?

I have an ATMEGA328p-pu arduino with an LED + shift-register strip circuit attached over SPI. When it turns on, it increases a variable in EEPROM to advance the display mode. We have the brownout ...
5
votes
1answer
154 views

Different behaviour when using single supercap vs several in series

I'm designing a circuit where I need a supercapacitor to continue powering the circuit for a few seconds after the main power has been removed. A simplified schematic of the circuit is shown below. ...
20
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 ...
2
votes
2answers
108 views

Need chargeable momentary 15 watt regulated voltage source

I'm working on a RF telemetry side-project that requires an amplifier IC to be run for about 5 seconds bursts between charges. The system is portable and runs off of a 3.3V battery that can supply ...
1
vote
2answers
130 views

How many watts will the resistor in this naîve PSU dissipate?

One would be inclined to think the average current on resistor R would be exactly the same as in the load L, but I'm not so sure of that fact, due to the effect of the (big, 1000uF+) capacitors. ...
3
votes
1answer
213 views

output filters for power supply design

I am trying to develop a design for a power supply design. At the output of my design is a diode rectifier with capacitive filter output. I've been told that I should expect to see an ESR zero or ...
5
votes
3answers
977 views

designing a power supply (zener) to achieve steady 6v (5.99 | 6.01)

UPDATE: my target is to obtain 6v as the voltage output. as you can see, it is 5.94 V, ive tried adjusting my variables yet it varies from 5.6 to 5.94 v, never did it reached 6v. what would be the ...
1
vote
2answers
338 views

Capacitor bank to smooth out current surges

I am thinking about building a capacitor bank between the PSU and load to smooth out current surges from electric motors. However, if the capacitors are discharging rapidly during a current surge, ...
3
votes
1answer
204 views

effect of output capacitance

I am wondering if anybody has more information about the effect of an output capacitor on a circuit? I.e. Does an output capacitor with (parallel) resistive load contribute any poles or zeroes, and ...
1
vote
1answer
164 views

Why sine wave UPS triggering surge protector again and again

I recently open up brother's APC sine wave UPS to fix and trying to repair some damage that usually happen over time due to age by replacing components I suspect one by one. When I start doing AC ...
3
votes
1answer
1k views

Fixing APC UPS buzzing noise

I have an APC UPS and one of the caps - an SIEMENS EPCOS 20uF 150V Capacitor - started making a buzzing noise. This seems to be a AC, non-electrolytic capacitor and most local stores have it priced ...
5
votes
3answers
242 views

Power supply design pattern with various capacitors

I'm seeing the following pattern for power supplies on the board I'm working on: What is the purpose of the capacitors? Why are they of different values? What is the purpose of the design pattern?
4
votes
2answers
214 views

Protecting low voltage high C capacitor with high voltage low C capacitor

With regards to "catching" very high voltage transients on a DC power supply, is it possible to use a small, high voltage capacitor with a current limiting resistor to catch the transient in order to ...
2
votes
1answer
194 views

Possible to use a Double Layer Capacitor (SuperCap) instead of Electrolytic?

I'm working with a 3V/100mA circuit design that requires short but infrequent bursts of nearly 200mA. A larger power supply is out of the question. A Capacitor plantation of about 4000uF would cover ...
-2
votes
2answers
245 views

Regulated A/C to D/C Power Supply

So im still a bit of an Electronics newbie. and was watching this video: http://www.youtube.com/watch?v=cyhzpFqXwdA I understood mostly everything, but even at the end.....the voltage ripple was ...
2
votes
3answers
541 views

Diagnosing cause of electrolytic capacitor failing

I am hoping somebody could help me diagnose the cause of failing electrolytic capacitors in a circuit. The context is a charger circuit, more specifically its power supply unit: Given a diode bridge ...
0
votes
1answer
122 views

THS6002 “Dual Differential Line Drivers and Receivers”. Output: 15 MHz

I made ​​a PCB with the THS6002 chip "Dual Differential Line Drivers and Receivers". I copied the application example of figure 59 in the datasheet (page: 34), with three differences: the transformer ...
3
votes
3answers
975 views

How practical would a car booster using supercapacitors be?

Currently car boosters (a portable unit charged of an outlet and then connected to the car electrical system to start a car when the car battery is dead) typically use batteries - lead-acid, Li-Ion or ...
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 ...
6
votes
2answers
440 views

Can I connect a capacitor in parallels to power supply of a router

In the building where I live, because of older wiring, the mains voltage frequently drops for a fraction of a second and this restarts my wifi router. I am planning to solder a capacitor in parallel ...
4
votes
3answers
576 views

HUGE capacitor recommended in datasheet for Audio Amp

I'm using the TPA3111 audio amplifier in a circuit of mine and I'm working on adding the appropriate capacitors. However, on page 18/19 of the datasheet TI recommends to use a 220mF capacitor on the ...
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
2answers
264 views

Power and ground configuration in a schematic

I have a schematic for a commerical circuit board, and I was curious about the following: ...
1
vote
1answer
410 views

Is it safe to keep on using AC adapter with a damaged output capacitor?

I was experimenting with my universal laptop adapter (Meind 100W) and when I switched it to 34V mode (while official max is 24V) the capacitor (25V) popped (the top opened and some white fibers spread ...
4
votes
2answers
508 views

Long supply line and capacitor to prevent voltage drop

I have a 30 feet line with DC supply 12 V. A motor on the end draws about 0.5 Amps initially (100 ms). It's logic shuts down because of the line's voltage drop caused by inrush current. A capacitor of ...
2
votes
1answer
374 views

Can I use a PET capacitor in a power supply? What's the difference?

I've noticed that certain types of capacitors seem to be used more commonly in certain applications. I've got a few over-sized 1uf PET caps that are a little too large for the application I originally ...
2
votes
2answers
297 views

Capacitor to provide power to a circuit during a very small interruption

I need some help in figuring out what size capacitor I need, and if my idea will even work. I have a small remotely-controlled helicopter, and a very small camera. I am trying to record video while ...
4
votes
3answers
546 views

Help with power-loss protection using capacitor

I designing a circuit will store log data to an SD card. The information will be coming form a parent circuit that this one plugs into. The parent circuit will supply 5V to my daughter card. The ...
12
votes
6answers
4k views

How to find the ESR of a capacitor

I am building a power supply circuit. The Switching Regulator calls for a low ESR output capacitor. What does "low" mean? How low? Also, how do I find or calculate the ESR for a capacitor whose ...
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 ...