Tagged Questions

1
vote
3answers
115 views

Charging a low-voltage high-C capacitor. Efficiently

I'm currently upgrading my wind-up torch - upon opening it, I found the manufacturers had been quite sneaky in that the circuit is EITHER windup OR battery powered - worse, the batteries are ...
6
votes
1answer
151 views

How do I decide what capacitor to use in a circuit?

I am using a voltage regulator and to get cleaner power, the datasheet recommends using a 0.33uF capacitor. However, it doesn't say what type it wants. Stupidly, I ...
0
votes
2answers
102 views

Voltage Regulation and Capacitors

Currently I am building my own AVR dev board, and I have been looking online about how to build the voltage regulator. I can build it, but I am curious as to why a capacitor is necessary. Also what ...
0
votes
2answers
81 views

What formulas do I need to use to design a voltage regulator circuit for a zigbee radio?

I've written the code for my zigbee radios, but now I face the obstacle of getting them onto a carrier board to allow access to VCC, GND, TX, RX via a 4 wire connector. The supply voltage is 3.712 ...
0
votes
1answer
88 views

voltage regulators and capacitors

So I'm new to electronics and was looking at some Eagle schematics when I came across the following voltage regulator schematic: My question is: would it be possible to change the regulator to ...
0
votes
1answer
195 views

Building a new dynamo bike light

So here is the deal, for the 2nd time in less than a year, my halogen bike light on the front has popped due to cold. This is rather bothersome and I can't find any nice inexpensive LED alternatives ...
1
vote
1answer
127 views

Are tantalums good for PIC Vcap?

I understand that ceramics are good at ESR but would like to know if tantalum would suffice for my application. Some 16 bit PICs require a >4.7uf cap (10uf recommended) low ESR cap for their internal ...
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 ...
0
votes
1answer
138 views

going from 5volt 1A to equivalent from a 3V CR2 Battery

I have a small camera with wifi that runs off a 3V CR2 battery. I'm trying to run it from line voltage. Could not find any small transformers that go to 3volt 750mA. I have an Apple transformer for ...
3
votes
1answer
202 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 ...
2
votes
2answers
411 views

Capacitor sizing on a voltage regulator output

I have an application in which an RFID reader demands 200 mA of current when it attempts to read an RFID tag. For some reason the current switcher power supply either can't supply enough current or ...
5
votes
2answers
611 views

Explaining a car voltage regulator circuit

I need to come up with a solution for a voltage regulator to be used in a vehicle, regulating ~12V from the car battery to 5V used by Atmel AVR microcontroller. I've found this schematic on the ...
0
votes
2answers
791 views

12V -> 5V 1A using L7805CV

I need to convert 12V (may vary from 11 to 14V - motorbike battery) to 5V 1A (microusb phone charger). I have the L7805CV positive voltage regulator. Which capacitors I need to connect at input and ...
3
votes
3answers
700 views

How much capacitance do I need in the input of LM78L05

I want to use LM78L05 as a fixed output voltage regulator as shown in the datasheet, as I cited below. My regulator is 2 meters away from the power supply filter. My input voltage is 24V, however this ...
-2
votes
2answers
244 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 ...
6
votes
4answers
326 views

Is soldering SMD capacitors directly to TO-220 regulator pins a good idea?

A while ago I read here that it's a good idea to have ceramic capacitors on the input and output pins of 78xx regulators and to put \$10 \mbox{ } \mu F\$ on the input and \$1 \mbox{ } \mu F\$ on the ...
4
votes
2answers
771 views

Which type of 100nF capacitor is best for 78xx regulator output?

I use 78L12 or similar voltage regulators in a few power supplies. I use them in their basic setup, see the picture: This diagram is common for all 78xx and 78Lxx regulators. It says that output ...
3
votes
3answers
883 views

How is ESR specified on ceramic capacitors?

I'm looking for a capacitor to use as the output cap with this regulator: http://uk.farnell.com/exar/sp6205em5-l-3-3/ic-v-reg-ldo-0-5a-3-3v-smd-6205/dp/9388338 It says it requires a 2.2uF capacitor, ...
2
votes
4answers
347 views

Understanding when to use basic Components

So I understand AVR assembly for the most part, and generally understand the overview of microcontrollers. but when it comes to specific components (besides the obvious stuff like resistors/batterys) ...
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 ...