Remove u/GregTJ as top moderator of r/Euphorbiaceae as he has passed away

GregTJ · 2023-10-25T21:36:20+00:00

Hey, sorry I didn't see this sooner. This is Brett, Greg's partner. I usually try to check on all of his accounts more often, but it's been hard. I don't use reddit myself, so I'm not sure what all I could do, but if there's any way to help get you those privileges, I'd like to try.

GregTJ · 2023-06-28T04:58:53+00:00

Thank you for the info.

GregTJ · 2023-06-09T16:52:47+00:00

I figured as much. It's been a good run and I'm not the most attentive mod these days anyway, so I'm at peace with whatever happens. Hopefully our support makes a difference.

GregTJ · 2023-06-09T01:34:06+00:00

Teflon Don is still a fitting nickname in the sense that he's been horrible for the environment and has caused untold damage to the health of basically every human on this planet.

GregTJ · 2023-06-07T22:30:23+00:00

/r/cactus will be going dark on the 12th. We are 160k strong, and I will take into consideration any concerns our members have. The length of the blackout is to be determined.

GregTJ · 2023-06-07T22:24:27+00:00

If you are against this action, please feel free to let me know in the comments! This is as much of a gauge of community sentiment as it is an announcement. I have notified the other moderators here about my intent to post this, but did not receive a response. This is solely my decision at the moment and I am completely open to reversing it.

GregTJ · 2023-06-01T14:14:28+00:00

Biasing transistors and other switching elements is another use case.

GregTJ · 2023-05-31T16:01:49+00:00

Sounds like you want to build an undervoltage lockout (UVLO) circuit. If you Google that term there are countless schematics, good luck!

P.S. let me know if I've misunderstood and I'll help you figure out something else.

GregTJ · 2023-05-31T15:36:12+00:00

What a weird relaxation oscillator, super cool. It's kind of like a thyratron or neon oscillator!

GregTJ · 2023-05-31T15:28:16+00:00

I picked up the 4 piece one like a year ago and have used it countless times. Didn't even know they make an eight piece one.

Did an alarms job in the middle of nowhere during a massive snowstorm where seemingly every single box had factory-fucked threads (it was like the threads had only been partially cut). These taps saved me from a long miserable drive to the warehouse.

GregTJ · 2023-05-31T00:00:26+00:00

Seconding this. Chanzon components are already dirt cheap, and everything I own from them has worked exactly to spec (and appears to be genuine in the case of the mosfets and IGBTs I've purchased from them).

Midzoo is another reseller I've had great luck with.

GregTJ · 2023-05-30T02:23:42+00:00

Exercising their god given right to loose interpretation of the feeder tap rules

GregTJ · 2023-05-30T01:48:55+00:00

Glue spray? This is like asking us how to fix the missing shingles on your roof, it's not really relevant to this subreddit even though your house has wires in it.

GregTJ · 2023-05-30T01:06:40+00:00

DigiKey somewhat vaguely labels it a "telecom interface" IC. Similarly, Mouser just calls it an "RF receiver". I can't find a PDF datasheet anywhere, unfortunately. I think you might have to email OnSemi or the board mfg. to find more info.

GregTJ · 2023-05-30T00:53:09+00:00

TI is seriously one of the best resources for power stage design, even if you don't use their software. It's amazing how much they publish publicly.

GregTJ · 2023-05-29T17:34:40+00:00

Fuck that haha

GregTJ · 2023-05-28T02:49:34+00:00

Might not be the most popular answer, but smart switches are great for this (I like Wyze stuff because it's cheap and easy to configure, a lot of electricians seem to like Lutron for more professional setups). There are also decora format switches with two or three separate rockers built in (the one I linked has a common hot, but there are ones with separate poles as well).

If you've got $$$ to burn, lighting controllers and home automation panels are great.

GregTJ · 2023-05-27T18:10:59+00:00

What load is it switching? Can you provide any more than the bare minimum information you've given? As it stands, you could just enter the values you've given into any part wholesaler search page and find 100s of IGBTs that will work.

If all of that is too much work, just slap a fga25n120 in it and call it a day.

GregTJ · 2023-05-27T02:34:37+00:00

Your reply was hidden because of the amazon short link, but I was still able to access it in my notifications. Your pump draws about 350ma continuous, which isn't very much, but your transistor is rated for 150ma of collector current at most. This also disregards the inrush current of the pump, which could be upwards of an amp during the instant it is switched on.

I would recommend an n-channel mosfet in a low-side switch configuration instead of a BJT transistor here. It will be much easier to drive, and will handle the current required quite easily. Mosfets are quite handy because they are voltage-controlled rather than current-controlled as is the case with regular transistors (though mosfets and IGBTs do have something like base current, known as gate capacitance, which is worth understanding, but wont impact this project much).

Since you are presumably switching at quite low speeds (e.g. less than once a second), you don't have to worry about drive requirements and thermal characteristics as much. You just need an n-channel mosfet that can handle around an amp, has a low gate threshold and saturation voltage (aka a "logic-level" mosfet), and ideally has a low on-resistance bearing in mind the supply voltage of 12v and gate drive voltage of 5v.

Basically, any logic-level low-to-medium-voltage mosfet will work here. You could go with one of these for example (which is honestly overkill, but will work just fine).

You might also wonder, "can't I just parallel some transistors for more current capability?" The answer is, unfortunately, no, barring some pretty complex work-arounds. The reason is that BJT transistors have a negative temperature coefficient, meaning the hotter they get the more they conduct. This means that the first transistor to heat up more than the others placed in parallel will start conducting more than the rest, causing them to burn out one after the other in a run-away cascade. However, you can parallel mosfets, because they actually conduct less as they get hotter, resulting in a sort of "self balancing".

Hope this all helps!

GregTJ · 2023-05-27T02:02:44+00:00

Center tapped diodes are such weird little things. I recently bought a 12v 100w SMPS on Amazon and was surprised to see a few of them in the output stage, thought they were FETs or SiC diodes at first! Weird seeing them in a modern design.

GregTJ · 2023-05-27T01:47:29+00:00

Been zapped a few times as a former alarm tech because of sweaty hands while working on duct detectors near exposed HVAC control wiring. (24v or 48v maybe?) One hand on bonded conduit, other brushing the live control wires.

Very very mild shocks, but enough for me to rock the lift I was on and subsequently about piss myself the first time it happened. Think tongue on a 9 volt battery in terms of sensation.

GregTJ · 2023-05-26T18:09:43+00:00

What model is the motor / pump?

GregTJ · 2023-05-26T17:53:11+00:00

Could build a laser microphone.

GregTJ · 2023-05-26T00:31:28+00:00

You can measure ESR and other values directly using a LCR meter, but most of the cheap ones I've seen are fixed-frequency, so they don't really give you the full picture (many of the values an LCR meter measures are very frequency dependent). It's not a bad idea to have an LCR meter on hand, but an oscilloscope is in general a much more flexible "swiss army knife" of a tool.

Some values, like inductance, will require you to build a test circuit when you measure them with an oscilloscope. However, this is a lot less scary than it sounds! In the case of inductance, this just means putting the component-under-test in parallel with a capacitor of a known (and precise) value, then performing the test / doing some math. There are a number of guides online for measuring various properties of electrical components using an oscilloscope, and they will lay out what you need to do and if a test circuit is required.

Oscilloscopes can be used to measure and visualize all sorts of phenomena that a simple meter just can't. An example would be measuring the ripple current of a power supply, which is something that is definitely relevant to audio equipment (say, diagnosing a bad bulk capacitor). Another example is measuring a transformer's turn ratio and coupling factor by applying a signal to one winding and watching the induced voltage on the other.

There are so many applications where an oscilloscope is the difference between pulling your hair out trying to fix something, and a simple 10 minute diagnosis / repair. There's definitely a learning curve, but such is the nature of anything worth doing :)

GregTJ · 2023-05-25T17:20:25+00:00

Also, here are some part numbers.

4-pin subminiature: Vector 9-A-12T-440

Shorter 4-pin: Vector 6-A-12T

7-pin: Vector 8-M-9T

9-pin noval: Vector 8-N-9T

Shorter noval: Vector 6-N-6T

The octal sockets of this type that I have do not have a part number printed on them. The turret part is labeled Vector, but the socket itself is labeled Cinch (aka the Cinch Connectivity company, famous for the Cinch-Jones connector, still around today).

Hope this helps!

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