# Tagged Questions

76 views

### How to drive a LED strip from AC power supply?

I have a LED strip (5050) and a sine-wave AC power supply of a sufficient wattage and the voltage regulated in a sufficient scale. What would be a good design of driving the LED strip from this ...
141 views

### Copper strips in chopper transformer

Do somebody know why there are large copper strips inside a chopper transformer that I've hacked and dissembled ? Does anybody know what is their purpose? What's the mathematical theory behind ...
99 views

### High current linear PSU capacitor requirements

Electrolytic caps have rated max ripple current (usually about 2A or so, even the "low ESR" ones). So, if I want to build a high current power supply (say 100A at 12V), I should use a lot of ...
404 views

### Calculations for a linear power supply

I've missed some classes and I'm struggling to do this. I need to "design a linear power supply with 12v output, with simple series regulator, providing a 2A current from 220V AC (60Hz)". I don't ...
530 views

### What is this white stuff inside this circuit board?

I'm having problem getting any output from this universal adapter for my older laptop, so I opened it up to see this rubber-like white substance inside, on top of the big 68uF 400V capacitor. A ...
3k 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) ...
362 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 ...
960 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 ...
342 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 ...
185 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. ...
7k 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 ...
138 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 ...
138 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. ...
252 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 ...
1k views

### Designing a power supply (zener) to achieve steady 6V ($\pm$ 0.01)

UPDATE: My target is to obtain 6V as the voltage output. As you can see, it is 5.94 V. I've tried adjusting my variables, yet it varies from 5.6 to 5.94V, never having reached 6V. What would be the ...
502 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, ...
293 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 ...
188 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 ...
2k 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 ...
281 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?
240 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 ...
209 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 ...
323 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 ...
788 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 ...
140 views

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

I made â€‹â€‹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 ...
2k 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 ...
7k 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 ...
531 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 ...
682 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 ...
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 ...
278 views

### Power and ground configuration in a schematic

I have a schematic for a commerical circuit board, and I was curious about the following: ...
461 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 ...
656 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 ...
433 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 ...
373 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 ...
668 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 ...