askelectronics

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collegefurtrader, in What creates resistance in a circuit?

Some resistance? Yes.

Significant resistance? No.

Susan_B_Good, in How to properly size a serial bulb for protection when troubleshooting a circuit?

You can make your own current-limited power supply, probably from bits and pieces you already have. Let's say that you have a 5v dc power supply and a hand full of rectifier diodes and resistors (various values and sizes).

Put a series chain of forward biased rectifier diodes and resistor(s) across your 6v supply. Choose enough diodes to give you a 3v output. Now choose a combination of series/parallel resistors to give you a 2v drop with a current of, say 100mA. You need 20 ohms - so that could be 5 x 100 ohm resistors in parallel.

The most current that can put out is the full 5v across 20 ohms - but at that point the output voltage will be near zero.

Bench supplies, well reasonable ones, allow you to set a current limit as well as an output voltage. At loads below that current limit - it operates as a constant voltage supply. At loads above - it operates as a "constant current" supply. You would set the output current limit to 100mA and that's the most that it will output.

Now the rectifier diodes plus resistor would allow the current to increase above 100mA, up to 250mA when the output voltage will be near zero (short circuited) - if you want better than that, then you can add a transistor and a few other components.

opensesame11, (edited ) in MOSFET as Radiation Detector

You could try connecting a current source to the source of the FET, connect the gate to a voltage reference, and connect the drain to a supply. Then the gate source voltage will be kept at threshold at all times and can be measured with a difference amplifier.

This could be done with a couple of op-amps provided they aren't adversely affected by the radiation.

Edit: Looks like blarbasaurus beat me to it.

duckythescientist, in Weird cable with USB A connector with 5 pins

Pics would be helpful

human_no_4815162342,

I am pretty busy this week, I am posting when I have breaks and I don't have it with me. When I'll have the time I will make a post with photos and measurements and I will probably also open it up.

Belgdore, in Weird cable with USB A connector with 5 pins

Sounds like you bought a crappy cable. Why not just buy a good one instead of disassembling and replacing stuff?

My guess is that it needs the fifth pin to trick some devices to think that it’s a 3.0 cable instead of a 2.0 with a c connector.

human_no_4815162342,

Type C 2.0 exists and is widespread and that is what I wanted, the issue is that it doesn't work as a 2.0 cable either. I like the liquid silicone exterior and I have a few connectors ready so if I like what's inside I may upgrade it. Otherwise I will recycle it and I already have better cables.

Belgdore,

Hey fair enough. If you are really concerned about what it if you could always reach out to the manufacturer

ConductiveInsulation, in How to properly size a serial bulb for protection when troubleshooting a circuit?

I've successfully used incandescent Bulbs in the past. They have barely any resistance when cold, which is the reason why they usually blow up when you turn them on.

For their size, usually I use more than the power the device will use but less than the wires can handle for a while. In your case id get a lamp with a E10 socket, for example 3.5V 0,7W.

Alternatively you can use a PSU with current limiting features.

leftascenter, in Safety tips when disassembling old electronics?
@leftascenter@discuss.tchncs.de avatar

Any bubbled up and leaking condenser may be acidic, don't touch it.

Soldering fumes are bad.

That's all I can think of.

Jode, in Safety tips when disassembling old electronics?

Discharge capacitors before fucking with them.

Swiggles, in Safety tips when disassembling old electronics?

Some old electronics use asbestos in heating elements or for shielding. Be careful when dealing with old hair dryers, coffee makers, stoves etc.

I don't see how there could be any in your tape recorder though. It's just what came to my mind when I read the title.

nilclass,

good to know for the future!

Susan_B_Good, in Safety tips when disassembling old electronics?

Wear trainers not sling backs. Molten solder and your tootsie don't go well together.
I turn the printed circuit board component side down and wave a hot air gun over the flip side, whilst tapping the board against the edge of work bench. The result is usually a cascade of components (and blobs of molten solder).

Very therapeutic. When I'm stuck trying to work out how to do something, when everything I have tried has failed miserably, I deconstruct something electronic. No, I keep well away from psychiatrists.

You (I anticipate) won't be doing this 9 hours a day, 7 days a week - most of the nasties are long term exposure ones, so a one-off should be fine. If anything ever irritates your eyes or throat, get out of there and ventilate the place.

MegaGoat, in Safety tips when disassembling old electronics?

There is the old thermal paste made of Beryllium oxide. Best not to eat it.

nilclass,

Best not to eat it.

dang... what else to do with the leftovers then?

Saigonauticon,

Grind it into dust, add sand, pour molten non-recyclable plastic into it (e.g. recyclable plastic with too many impurities). Market it as a weighted ballast material e.g. for the base of IKEA lamps.

Saigonauticon, in Safety tips when disassembling old electronics?

Mostly I just work in a well ventilated area. Oh and for sure disconnect power before desoldering anything.

Other than that, I avoid taking apart microwaves (beryllium, high voltage), anything with a CRT (imploding glass, high voltage), and high voltage transformers (transformer oil, high voltage). Also any medical equipment (chemical hazard, radiation hazards, biohazard, high voltage, imploding glass). Oh and no unexploded munitions for reasons that should be obvious (people still salvage these in my country and it sometimes doesn't end well).

I find a hot air rework station+tweezers a much faster way to salvage than jamming a hot iron into boards. Also lets you salvage SMT components, which are most of the better parts these days. For 1970s stuff, it's mostly through-hole, I'd test the parts before trying to reuse them. Capacitors especially. Got to love those big transistors from our side of the Iron Curtain though.

Saigonauticon, in Weird cable with USB A connector with 5 pins

In my experience, if they don't include the conductor in the connector, there will generally not be a wire for it in the cable. So replacing the USB-C connector is probably not going to add any functionality.

I have a stack of USB-A to USB mini/micro cables that are a bit like this. Two conductors, only do charging. So if I replace the connector, there's no wire to connect the D+ / D- lines to. It's quite possible the manufacturer of your cable had some similar or otherwise reduced feature set in mind, and wanted to save 5 cents of copper.

I also have some cursed cables that have normal ports, but only two wires inside the cable (power/ground), or are otherwise out-of-spec in ways that make the data lines mostly fail. These have wasted quite a bit of my time over the years.

human_no_4815162342,

I only need a USB 2.0 cable mostly for charging, I have better cables, I chose this one for the liquid silicone outer layer. Of course if the wires inside are less than four or too thin I won't waste USB connectors (that I already have, I would not order them for this) and I will recycle it.

PCChipsM922U, in SBC UART debug troubleshooting
@PCChipsM922U@sh.itjust.works avatar

It's probably just the converter... something misconfigured in the drivers or... who knows. Try and see if you get the same garbled data in Windows and Linux (binary check). If they match, it's something hardware wise.

Back in the day, yes, the Chinese USB to Serial/Prallel converters were terrible, no doubt there. But, over the years, they've gotten surprisingly good. In fact, I picked one up a few weeks ago (as you said, about $5), works like charm.

th_in_gs,

I suspect your serial converter is expecting a ‘real’ RS232 signal, with its old-school now-weird voltage levels.

Your USB serial adapter is probably using 5V or 3V so-called ‘TTL’ signaling (which in the real world is mostly cross-compatible between 5V and 3V)

Good explanation here: https://www.sparkfun.com/tutorials/215

th_in_gs, in SBC UART debug troubleshooting

I suspect your serial converter is expecting a ‘real’ RS232 signal, with its old-school now-weird voltage levels.

Your USB serial adapter is probably using 5V or 3V so-called ‘TTL’ signaling (which in the real world is mostly cross-compatible between 5V and 3V)

Good explanation here: https://www.sparkfun.com/tutorials/215

MaximGun,

Yeah this must be it. Thanks.

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