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Search: Posts Made By: redwire
Forum: Equipment Usage, Soldering, Techniques, and Reviews Today, 11:27 AM
Replies: 75
Views: 1,008
Posted By redwire
Re: DPS5020 dual power supply build

It happens in all transformers, residual magnetism in the core. The only way to demagnetize is apply a lower voltage sine wave and then slowly dial voltage down. It's kind of like demagnetizing a...
Forum: Equipment Usage, Soldering, Techniques, and Reviews Yesterday, 02:26 PM
Replies: 75
Views: 1,008
Posted By redwire
Re: DPS5020 dual power supply build

The core is steel, it can stay magnetized for a very long time.
Forum: Equipment Usage, Soldering, Techniques, and Reviews Yesterday, 11:34 AM
Replies: 75
Views: 1,008
Posted By redwire
Re: DPS5020 dual power supply build

Big power transformers, they can be magnetized when you switch off power.
The flux alternates between N and S at 50/60Hz but say you unplug it when the core is at peak N. Then you plug it in for...
Forum: Equipment Usage, Soldering, Techniques, and Reviews 07-17-2019, 02:54 PM
Replies: 75
Views: 1,008
Posted By redwire
Re: DPS5020 dual power supply build

If the primary fuse is slow-blow and it can handle it, then I would keep it simple.
Above around 20,000uF is when I add a soft-start to a mains transformer, or just listen to the mains wiring rattle...
Forum: General Electronics Technical Discussion 07-14-2019, 08:34 PM
Replies: 6
Views: 102
Posted By redwire
Re: Step-Down Buck Charging Board XL4015 ADJ Lithium Battery Charger Converter Module

chinese amps are different than American amps, although Ampère is a French mathematician and physicist.

At 5A output it is 87% efficient at best, so around 4W of heat dissipated in the IC for a...
Forum: General Electronics Technical Discussion 07-14-2019, 01:28 PM
Replies: 3
Views: 107
Posted By redwire
Re: USB Voltage and Current Tester Capacity What do you think about this

Pretty fancy 2.6" IPS 320x240 LCD.
https://diykitsblog.com/obzory-i-testy/t50n-dvojnoj-usb-tester-ot-100mhz.html did a teardown of one, probably older firmware. use google translate.

RDTech Store...
Forum: General Electronics Technical Discussion 07-12-2019, 01:57 PM
Replies: 10
Views: 172
Posted By redwire
Re: Destroying or not destroying analog meter movements

The meter coil is basically acting as a wire-wound resistor at that point, making heat.
Doing some math using a Simpson 260-6 for numbers: Full-scale takes 50µA (250mV) or 12.5uW. The meter coil is...
Forum: General Capacitor Questions & Issues 07-11-2019, 07:57 PM
Replies: 20
Views: 213
Posted By redwire
Re: Question about SMD Crystal and proper capacitor placement / pin connections

You got a part number for the crystal?

Number one when doing MCU PCB layout is having the crystal close to the MCU, shortest traces you can get away with, AND no noisy traces running next to them....
Forum: General Electronics Technical Discussion 07-11-2019, 07:52 PM
Replies: 47
Views: 672
Posted By redwire
Re: Running a microcontroller in car - power supply aspects

I was showing two possible ways to go for the inputs.
If the 1N4148 was replaced by a 5.1V zener, you see the LED will turn on first at 1.3V and the zener can never see 5.1V

Resistors are OK. 20k...
Forum: General Electronics Technical Discussion 07-11-2019, 01:01 PM
Replies: 47
Views: 672
Posted By redwire
Re: Running a microcontroller in car - power supply aspects

Here are two common ways to run digital inputs to an MCU. The hassle is protecting for overvoltage spikes from static electricity or switching inductive loads, like blower, wiper motor, ignition etc....
Forum: General Electronics Technical Discussion 07-11-2019, 12:50 PM
Replies: 10
Views: 172
Posted By redwire
Re: Destroying or not destroying analog meter movements

Analog multimeters have clamp diodes across the meter movement for protection.
The meter will still peg overloaded but the diodes limit what the meter movement gets.
It's usually one pair of...
Forum: Troubleshooting Power Supplies and Power Supply Design 07-10-2019, 12:20 PM
Replies: 16
Views: 1,235
Posted By redwire
Re: Recapping Tektronix 2235 PSU

Updated the spreadsheet. Finally figured out the typo for C956 scope model vs value. 10uF 2235A, 270uF 2235 as guy232 pointed out.
Forum: General Electronics Technical Discussion 07-09-2019, 06:53 PM
Replies: 47
Views: 672
Posted By redwire
Re: Running a microcontroller in car - power supply aspects

I think the worry is the 5V buck-converter could fail and overvoltage everything, roast Arduino for dinner.

Arduino Pro Mini (5V version) uses MIC5205...
Forum: General Electronics Technical Discussion 07-09-2019, 02:27 PM
Replies: 47
Views: 672
Posted By redwire
Re: Running a microcontroller in car - power supply aspects

The schematic looks really good for first time in KiCad.

Some things to maybe consider:
Put the switches after the fuse, because switch/door wiring always shorts out.

The zeners on the opto's...
Forum: General Electronics Technical Discussion 07-07-2019, 09:07 PM
Replies: 34
Views: 3,299
Posted By redwire
Re: Blendtec smoother 13 repair.

I saw carbon brushes from specialty shops on Aliexpress "carbon brushes" but you have to know the dimensions. They're a dollar.

For break-in, connect a DC power supply or AC adapter or variac for...
Forum: Troubleshooting Power Supplies and Power Supply Design 07-07-2019, 11:45 AM
Replies: 11
Views: 222
Posted By redwire
Re: Smart Charger 29 volts @ 1 amp how do I change it 25 volts

It's very cheap power supply - there is no opto-coupler+voltage reference (i.e. TL431) to provide feedback to the SMPS IC and control the DC output voltage.
It might just regulate from the aux...
Forum: Equipment Usage, Soldering, Techniques, and Reviews 07-03-2019, 11:47 AM
Replies: 18
Views: 495
Posted By redwire
Re: KSGER STM32 T12 soldering stations

When I pried, the pins slid right out of the GX12. They do not have collars (like in pic) to grab the epoxy, it's a cheap connector from KSGER.
Forum: General Electronics Technical Discussion 07-03-2019, 11:41 AM
Replies: 16
Views: 388
Posted By redwire
Re: Variac 20 amp advice?

For my variac project, I took apart that mini voltmeter and brought out the Vsense wire, so it's three wires now. It's powered off the input mains but measures the variac output, so I can dial down...
Forum: General Electronics Technical Discussion 07-03-2019, 11:38 AM
Replies: 29
Views: 390
Posted By redwire
Re: Zero to Expert in pcb design

No, I'm afraid you'll actually have to do some work.
Nothing will auto-check a design beyond the wiring (netlist) and some basic spacings and clearance.
PCB CAD programs are all very basic. Every...
Forum: Equipment Usage, Soldering, Techniques, and Reviews 07-02-2019, 09:02 PM
Replies: 18
Views: 495
Posted By redwire
Re: KSGER STM32 T12 soldering stations

The GX12 has 1.6mm pins and the desoldering tools I have couldn't clear the holes. No tips fit over the pins close spacing. I thought hot air would melt everything around it like the JST power...
Forum: Troubleshooting Audio Equipment 06-30-2019, 10:05 AM
Replies: 3
Views: 144
Posted By redwire
Re: Marantz 1030: Extreme Bias Voltage and Distortion on Left Channel

I think it's a quasi-complementary output stage, so the bias works differently.

To check the transistors I would compare readings between channels (power off, with multimeter on diode test) of the...
Forum: Equipment Usage, Soldering, Techniques, and Reviews 06-30-2019, 10:02 AM
Replies: 18
Views: 495
Posted By redwire
Re: KSGER STM32 T12 soldering stations

Anyone know the T12 handle components? They ship two NTC thermistors and two different motion switches, a ball shake switch and a mercury switch.

The black blob NTC I have only seen on a...
Forum: General Electronics Technical Discussion 06-25-2019, 04:48 PM
Replies: 5
Views: 197
Posted By redwire
Re: Help to identify SMD Zener diode

Not sure if SOD-123 or SOD-323 package.
Diodes Inc DDZ5V1BS (https://www.diodes.com/assets/Datasheets/ds30414.pdf) SOD-323
Diodes Inc DDZ5V1B (https://www.diodes.com/assets/Datasheets/Ds30407.pdf)...
Forum: General Electronics Technical Discussion 06-24-2019, 12:35 PM
Replies: 21
Views: 414
Posted By redwire
Re: Found a transformer at a thrift store and am curious...

OP you have a 10W 70 volt line audio matching transformer. It is used for bigger paging and PA speaker installations.

It is not suitable for use as a mains power transformer. It does not have...
Forum: General Electronics Technical Discussion 06-23-2019, 03:48 PM
Replies: 22
Views: 367
Posted By redwire
Re: Dryer Motor Possibly Short Circuiting

Just to be clear, you have the same bad connection at a relay terminal on the PC board as the pics below? Bosch dishwasher that has bad connection just like your dryer pic.
It's a common problem in...
Showing results 1 to 25 of 500

 
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