The isolation tag has no wiki summary.
19
votes
3answers
2k views
Why are the high voltage overhead power lines with the same potential being isolated?
Photo #1
Photo #2
Photo #3 - A zoom of Photo #1
Photo #4 - A zoom of Photo #2
I shot these photos while travelling in a highway. In each line-group has three separate lines. I think that the ...
14
votes
4answers
2k views
Why is it important for mains power supplies to be isolated?
In all the computer power supplies and other power supplies I've taken apart, I've noticed they are fully isolated from the mains. Galvanic isolation through transformers, and often optical isolation ...
10
votes
3answers
732 views
Cellphone charger has no transformer?
I opened up a really tiny mobile phone charger I have, to see how it is designed. The entire "charger" is integrated into a small 2-pin mains plug, 1 x 1.25 x 0.5 inch, that has an USB socket for the ...
9
votes
1answer
584 views
Why does TO-220 79xx voltage regulators conduct the input voltage to the heat sink?
I find it somewhat dangerous to connect a large heat sink on 79xx series voltage regulators. Because they transfer all the negative voltage to the heat sink. Why just they didn't make the 2nd pin of ...
7
votes
2answers
1k views
What values of resistor and capacitor to use for AVR reset pin isolation?
Background...
I'm a newbie to AVR applications. I recently built two ATTINY13-based circuits (glorified LED blinkers) which worked correctly (independently) on the breadboard. When I combined them on ...
7
votes
2answers
226 views
Isolation transformer to reduce speaker pop
I have some computer speakers which suffer from the following problem:
when switches flip in certain devices in the house, like the thermostat on a radiator or the refrigerator, the speakers will emit ...
6
votes
4answers
570 views
Sensing DC motor current
I am allowing the current through a DC motor to flow through a small resistor and measuring the voltage across it. I need to give this analog Voltage to an ADC of micro-controller to do some signal ...
5
votes
4answers
468 views
how to electrically isolate a PCB from a heat sink
I have a set of LED driving lights on my motorcycle that must be wired through a ground-leg pulse width modulation dimmer. The problem is the mounting bracket for the lights is grounded, so the lamp ...
5
votes
3answers
392 views
Cutting the ground wire in an isolation transformer?
I bought a non-tech isolation transformer (500w), which I planned to cut the earth mains ground from the output, but leave the chassis grounded; however, when I opened it up I found the output outlets ...
5
votes
1answer
118 views
Determining if a power supply is isolated?
I've been looking for a low cost adapter I can use to power some electronic circuits I'm playing with. Pretty much the only requirement I have at this time is that the adapter is mains isolated for my ...
5
votes
1answer
2k views
Is galvanic isolation of Hi-speed USB impossible?
I have a USB isolator which provides galvanic isolation of a USB device from my PC, but only works for low speed and full speed USB. I can't find any alternative electric isolators which do provide ...
5
votes
2answers
647 views
Isolation Transformer
When a function generator is used to power a full wave rectifier an oscilloscope will not show the correct output due to a shared ground. A half wave is displayed because one of the diodes is ...
4
votes
3answers
123 views
Digital Isolation comparison
I am currently using ADuM4160 by Analog Devices as a USB isolator.
However, this part is EXPENSIVE. I was wondering if anyone thinks it can be replaced with ADuM2200.
Any reason why this wouldn't ...
4
votes
1answer
484 views
Best way to measure 230VAC
I'm trying to design a circuit to measure power of 230VAC (MAINS), with the ADC of a small MCU.
I have designed the part of the circuit to measure current, but my solution to measure voltage is ...
4
votes
3answers
210 views
Why are the pins on the official arduino motor shield so long?
Here is the Official Motor sheild website.
The shield has pin connectors at the bottom that are 2x longer than on any other shield I've seen. Why is that?
4
votes
3answers
828 views
Why is power supply from electrical utility referenced to earth?
In response to the question Basic Training for working with 120V AC zebonaut had replied that "A regular wall outlet is referenced to earth" and this provides the close loop for the circuit to ...
4
votes
2answers
659 views
Isolation transformer and scope when troubleshooting SMPS
I have a simple question, when troubleshooting a SMPS is highly adviced to use an Isolation transformer. But my question is this, if im using a scope to troubleshoot the "hot" side of my SMPS, both ...
4
votes
1answer
198 views
How is pouring water addressed in high-voltage electric transport systems?
An electric train is typically powered with something like 1,5 kilovolts of direct current of something like 25 kilovolts of alternating current. In my experience electric device manufacturers charge ...
4
votes
2answers
217 views
DC/DC isolated supplies in series for higher voltage?
Can I chain two isolated DC/DC supplies together for a higher output voltage? (Say, a 48V and a 12V to get 60V?) They'd be fed from the same 24V DC source.
I've asked a related question before ...
4
votes
1answer
115 views
how to test isolation of DCDC convertor?
I have an isolated DC-DC convertor which boasts a 1.5kV isolation. I have a PCB made along with the additional components it requires. How can I test it?
4
votes
1answer
232 views
Isolation for microcontroller that is off
I have a design where power savings is a huge issue and even the lowest power sleep mode of the \$\mu\$C is too much quiescent current (30 \$\mu\$A). I'm aware of many and have used \$\mu\$Cs in the ...
4
votes
2answers
214 views
Electrical Isolation
I've been reading about the EIA-485 standard and they talk about how even with twisted pair wire they need a 3rd connection for common because sometimes the devices need to be isolated. I was thinking ...
4
votes
2answers
96 views
When is it appropriate to galvanically isolate components/subsytems?
As the question implies, how do you determine when it is appropriate to galvanically isolate parts of the same electrical system from one another?
For example, I'm currently constructing a tube ...
4
votes
1answer
352 views
How should I isolate AC and DC on a small PCB?
I am designing a small PCB (1"x1") and it will have some DC logic traces (5V and GND) and some high frequency AC power traces (100V 1000Hz 50mA). Are there any special considerations I need to take ...
3
votes
3answers
211 views
Isolation of watch crystal from ICSP
I'm working on a project which uses a PIC with a 32kHz watch crystal attached to Timer1. Unfortunately, the chip I'm currently using, PIC16F1827, shares the T1OSI & T1OSO pins with ICSPCLK & ...
3
votes
3answers
213 views
Sensing signal on a power line from high side
I have a circuit design as above. I'm trying to sense the voltage difference accross the \$ 0.1 \Omega \$ resistor. I physically connected the sensory circuit to the low side of the AC line, and saw ...
3
votes
3answers
141 views
Mains triac safety circuit design
I am investigating using a triac instead of a relay to control 250V 10A devices.
However all the 600V 16A triacs come in TO-220 packages.
According to AS/NZS 3100 and AS/NZS 60335.1 I need at least ...
3
votes
2answers
210 views
How to properly isolate multiple power supplies
Say you have a single 110V AC supply and need to use it for a number of devices, each requiring very different characterists. For me personally these are: a direct use of the 110V AC supply for a ...
3
votes
4answers
247 views
Measuring voltage while maintaining isolation
I'm building a variable power supply, and want to provide the ability to digitally measure the outputted voltage and current. The digital power supply used to drive the ADC, microcontroller and ...
3
votes
3answers
330 views
home brew isolated oscilloscope lead
The ground clip for an oscilloscope lead is normally connected within the instrument to the power supply earth, and there are surprising circumstances where this could matter. The situation is very ...
3
votes
1answer
144 views
USB + Power: Isolate or not?
I am working on an adapter that will allow a device to be connected to both a PC and external power supply. I am wondering if I will need to isolate the 2 5V supplies with a DC/DC converter and some ...
2
votes
1answer
113 views
Are dual MOSFET devices isolated from each other? If so, to what degree?
I am using an OnSemi NTGD3148N dual MOSFET in a project. I cannot find a specification anywhere in the datasheet stating the isolation between the devices; and this holds true for most dual MOSFETs ...
2
votes
3answers
964 views
Switching 120V AC with Digital Logic on Isolated Power Supply
Context: A digital phase-controlled light dimmer system.
120V AC mains
I use an isolating transformer (and rectifying circuit) to generate +12V and +5V DC rails.
I want to use reverse phase ...
2
votes
1answer
34 views
How do I (optimally) connect Elk-924 (high sensitivity relay board ) to DSC PGM output (sinks to ground)
This sounds like a very specific question, but I think it boils to a generic one -- not at all specific to this equipment. But it will take a bit of backstory to get there.
My background, btw, is ...
2
votes
3answers
119 views
DC-DC isolation for my car stereo… Where do I start?
I recently noticed that my jeep's stereo whines with a frequency that seems proportional to the rpm of my engine (and alternator), and is louder when my headlights are on.
If my stereo was powered ...
2
votes
0answers
38 views
Isolation between cells for battery charging & testing
I want to charge Lipo battery packs and possibly other chemistries too. Six cell packs for starters. But hope to handle more and less. Perhaps a lot more cells. For electric vehicles, skateboards, ...
1
vote
2answers
336 views
what would be the most suitable components to replace some relays?
I'm working on an electronic product based on a microcontroller that must be able to control a series of actuators: 230V AC motors ON/OFF, 24V DC motors ON/OFF, 80V/20A heating element ON/OFF. The ...
1
vote
1answer
247 views
GPIO input connected to garage door button
I know there are other GPIO / Garage door related questions, but this is not a duplicate- I need to read the status of the garage door button, not a garage door sensor.
I would like to connect the ...
1
vote
1answer
162 views
Isolating BNC connector from test shield
For my project, I need to have BNC connectors on the test metal shield. So what I did so far is drilling holes, and mounting BNC connectors on it:
I used some hot shring on the part which passes ...
1
vote
1answer
259 views
How close can I place two transformers?
I need to place two of these transformers in a case. How close am I allowed to place them? Can they touch each other (of course, they will be electrically isolated)? Is their orientation with ...
1
vote
3answers
189 views
How to hook up an FPGA to a component that has a different power supply?
I recently programmed my FPGA with a logic analyzer core for the purpose of reverse engineering a crappy modem I have. I found on it what I think is either JTAG or TTL-serial pads. There are 4 blank ...
1
vote
1answer
182 views
Augment battery-run device power with 100mA solar cell?
I may be running a microcontroller for an extended period of time in a portable manner under battery, but do not want its life to be reduced by a silly load such as an LCD screen (5v + backlight) ...
1
vote
2answers
80 views
Dirt cheap 3-12v DC/DC isolatior chip?
I'm creating a box that will have an external TTL trigger. I want to isolate my box's power/ground from that of the triggering device.
Obviously, an optoisolator is the way to go (eg. PS2502).
...
1
vote
2answers
207 views
How can I do A/D conversion with isolation?
I have to sense a voltage range of 0-25V dc and send to the ATMEGA 32 microcontroller. I want to use a voltage divider for sensing the voltage. But the problem is isolation is required between the ...
1
vote
2answers
270 views
Isolation transformer weirdness
I recently posted a question about cutting the ground wire in an isolation transformer to make it truly isolated. After reading the responses, I decided the best advice was to reconnect the ground ...
1
vote
1answer
466 views
Need to isolate my ammeter (measuering and powering the unit from same power source)
I have a problem and Im not sure what the best way is to address this. I converted an ATX PC power supply to use as a lab power supply I installed a digital volt meter and a digital ammeter. To power ...
1
vote
0answers
75 views
How to Isolate Low Voltage Control Circuit from High Voltage Power Circuit?
Didn't have a lot of success google searching...
Can anyone give me a brief run-down of some methods I could use for this?
I want to drive a MOSFET or BJT with a 12v 555 circuit or oscillator. ...
0
votes
2answers
272 views
Sixteen 100v isolated power supplies
I need to create sixteen isolated power supplies on a single PCB.
Input voltage 9v DC.
Output voltage 100v DC.
Output current 10mA each.
No precise regulation needed.
Efficiency not terribly ...
0
votes
3answers
960 views
How to make two isolated power sources from one source?
I need to have two electrically isolated power sources.
Here are the details of the application: http://revolectrix.fmadirect.com/support_docs/item_1377.pdf page 26:
I need to make this work with ...
0
votes
1answer
46 views
How can I isolate a power well to reduce noise
I am designing a digital board which will drive a very coarse (simple on-off) high[er] current speaker. I am worried that the switching of the speaker will cause noise in the power supply driving it. ...
