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Forseti
May 26, 2001
To the lovenasium!


longview posted:

If you swap TX/RX every time, it's still a 50/50 shot if it being right. (vs. 0% if you don't )

In the spirit of having to deal with managers trying to run software projects like hardware (gently caress you, waterfall), now is my chance to flip the tables!

Simply label the pins with a variable name, like X and Y! Then include a piece of paper with the legend and change it if you need to. Bing bong, so simple

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silence_kit
Jul 14, 2011


Dewgy posted:

From what I understand about crystal charging, “meditation” is an interesting choice of phrasing for the process.

Lol

Rescue Toaster
Mar 13, 2003


Has anyone ever sent off a multimeter for calibration? At work the test equipment guys just come and whisk them away. But I got a decent deal on a used Keithley 2000 and my Agilent handheld also needs cal.

So I'm considering using one of the mail-in cal labs like https://www.custom-cal.com/Test_Equipment_Calibration.aspx. Any trip reports for something like this?

babyeatingpsychopath
Oct 28, 2000
Forum Veteran

Rescue Toaster posted:

Has anyone ever sent off a multimeter for calibration? At work the test equipment guys just come and whisk them away. But I got a decent deal on a used Keithley 2000 and my Agilent handheld also needs cal.

So I'm considering using one of the mail-in cal labs like https://www.custom-cal.com/Test_Equipment_Calibration.aspx. Any trip reports for something like this?

Find a cal lab local to you. Prices come WAY down if you can drop off and pick up in person. Get a price quote up front. I decided to calibrate my meters and they asked if I had any torque wrenches or pressure gauges, because they were running a special: three meters, get another tool free! So I now have a calibration report for my harbor freight torque wrench.

Forseti
May 26, 2001
To the lovenasium!


babyeatingpsychopath posted:

So I now have a calibration report for my harbor freight torque wrench.

So how is it? Does it stay consistent across the range? Beam type or digital?

Rescue Toaster
Mar 13, 2003


babyeatingpsychopath posted:

Find a cal lab local to you. Prices come WAY down if you can drop off and pick up in person. Get a price quote up front. I decided to calibrate my meters and they asked if I had any torque wrenches or pressure gauges, because they were running a special: three meters, get another tool free! So I now have a calibration report for my harbor freight torque wrench.

Unfortunately there is nobody local. Our company has the only cal lab in town and they're not setup for anything except the specific meters they support and they're not allowed to do personal equipment.

babyeatingpsychopath
Oct 28, 2000
Forum Veteran

Forseti posted:

So how is it? Does it stay consistent across the range? Beam type or digital?

Beam type. It's hilariously off below 15% of range, within 5% for the rest. Within 1% at the setting I bought it for. I think the cal guys got a kick out of running the test on what I have to assume is an unusual tool for them. The shop snap-on torque wrenches we typically sent them were 1% across the entire range, and had been for up to a dozen years for some of them.

Cory Parsnipson
Nov 15, 2015


I want to use some through hole sockets on a PCB so I can put something expensive on the board and still take it off without having to solder it. For example, an Arduino that has male pin header (uh, standard size? 0.65mm?) on it that I'm going to take off later and re-use anyway.

1. Is this going to do what I think it does?
2. Do I need to worry about the thickness/shape of my pin header vs the socket? It feels like everything is standardized to one size.
3. Also, is this something I can break to size like the other pin header stuff?

ante
Apr 9, 2005

SUNSHINE AND RAINBOWS

Those are round-pinned machine headers, and I'd avoid them all the time. More common headers, including what comes on Arduinos, have square pins and won't fit.


Just searching 0.1" headers on aliexpress/ebay/amazon will get you excellent deals on things that are good enough. And you can just cut them to size. Male headers break away easily, but female ones are usually solid, I just use snips to cut them to length.

Something like this:

https://www.digikey.com/en/products/detail/chip-quik-inc/HDR100IMP40F-G-RA-TH/5978223

Cory Parsnipson
Nov 15, 2015


ante posted:

Those are round-pinned machine headers, and I'd avoid them all the time. More common headers, including what comes on Arduinos, have square pins and won't fit.


Just searching 0.1" headers on aliexpress/ebay/amazon will get you excellent deals on things that are good enough. And you can just cut them to size. Male headers break away easily, but female ones are usually solid, I just use snips to cut them to length.

Something like this:

https://www.digikey.com/en/products/detail/chip-quik-inc/HDR100IMP40F-G-RA-TH/5978223

I have a lot of that. Perfect.

KnifeWrench
May 25, 2007

Practical and safe.



Bleak Gremlin

Cory Parsnipson posted:

I have a lot of that. Perfect.

Out of curiosity, and with no judgment, what did you think they were for? Or was it just a case of not seeing your nose right in front of your face until someone reminded you?

Martytoof
Feb 25, 2003

 
 




I've been trying to salvage connectors and other bits from a pair of old, dead Amiga 500 boards to use in my A500++ project and let me tell you what I've learned:

Unsoldering connectors is the bane of my existence. If I could readily source board mount DB23 connectors I wouldn't even bother.

So I guess I'm asking for any tips you guys may have on desoldering board mount connectors. The high heat sinking is a problem. I have one of those cheap desoldering guns which works fairly well I'll admit, to free the individual electrical pins out, but getting the mechanical connection pins desoldered is a pain because they're usually around much larger holes and sink the heat much more.

It'll be a labor of love I guess.

Cory Parsnipson
Nov 15, 2015


KnifeWrench posted:

Out of curiosity, and with no judgment, what did you think they were for? Or was it just a case of not seeing your nose right in front of your face until someone reminded you?

I have them packed away in boxes within boxes cause I've never had to use them. I got a whole bunch of both a really long time ago but I only used the male headers. I was also looking online and came across the idea of a DIP socket so I searched "removable pin header socket" and got to the part I linked in the previous post.

e. Maybe experience level is relevant too. I'm mostly used to programming, some breadboarding, and other equally technical pursuits such as watching TV and eating hot chip. It might be more self explanatory if you found me trying to remove a nail with my bare hands while having a hammer in my pocket, which would be more baffling if it happened to an expert like, say, if Adam Savage suddenly forgot how to use a wrench in the middle of his show. *queue concerned looks from his colleagues*

Cory Parsnipson fucked around with this message at 19:45 on Apr 9, 2021

Stack Machine
Mar 6, 2016

I can see through time!


Fun Shoe

Martytoof posted:

I've been trying to salvage connectors and other bits from a pair of old, dead Amiga 500 boards to use in my A500++ project and let me tell you what I've learned:

Unsoldering connectors is the bane of my existence. If I could readily source board mount DB23 connectors I wouldn't even bother.

So I guess I'm asking for any tips you guys may have on desoldering board mount connectors. The high heat sinking is a problem. I have one of those cheap desoldering guns which works fairly well I'll admit, to free the individual electrical pins out, but getting the mechanical connection pins desoldered is a pain because they're usually around much larger holes and sink the heat much more.

It'll be a labor of love I guess.

I say this every time it comes up but get a temperature controlled iron like a Weller or a Hakko or something. The closed-loop control means you get an effectively very high thermal conductivity to wherever the temperature sensor is even though the actual iron can be very small. The temperature just won't drop as much and will recover much faster than a non-controlled iron when you stick it onto some sort of heat sink, so it will just melt solder more effectively. Blowing/sucking the solder out of the holes will still be a pain in the rear end but if the board is already a write-off feel free to tug your connectors out with a little extra force. It'll maybe pull out the plated through holes from the board along with its pins but you can clean those off. Also if you carefully cut the board into pieces with a dremel or similar (just try not to grind up any solder into inhalable dust!) you can pop the pins out one at a time while the solder is melted which is a million times easier than getting the whole thing free enough to pull out cold.

Speaking of pulling components while the solder is melted, a thing I have done in the past is warming the solder joints with a propane torch or heat gun (paint dryer type, not solder rework type) and tugging on the component with pliers. This completely destroys the board but the parts are usually salvageable.

Martytoof
Feb 25, 2003

 
 




Thankfully I ended up buying both a TS-80P and a TS-12 ksger station so I am awash in temperature controlled gear. It sounds like this is just going to be a pain in the rear end and that's just part and parcel of what I'm trying to do. Both of these boards are trash so I'm OK damaging them, it's mainly the components I want to salvage without too much harm

Stack Machine
Mar 6, 2016

I can see through time!


Fun Shoe

Yeah I'm by no means a through-hole soldering expert but every time I try to de-solder something it seems to take some combination of a lot of effort, destroying the board, or destroying the parts I'm removing. This is kind of what lead to my conversion to hot air and surface mount for prototyping, since it's easier to get all of the solder to melt at once and lift parts off the board.

Foxfire_
Nov 8, 2010



Preheat the board and use good solder wick

Heat flux is proportional to the difference in temperatures. Soaking the entire board to 75-100C will make it a lot easier to get heat into the pins without other stuff sucking it away. Modern connector plastics would generally be fine at those temperature indefinitely, I would expect older Amiga-era ones would also be fine. You can build an okayish cheap uncontrolled preheater with a hotplate and a piece of aluminum to spread heat out, then adjusting till it's hot but water doesn't boil off immediately.

ante
Apr 9, 2005

SUNSHINE AND RAINBOWS

I like to lock vice grips onto connectors to give them some weight, and then hit the pins with a hot air gun with heat and airflow turned way up. They'll soften and the connector will just fall off.


Make sure they're covered in lead solder, too, not tin

Shame Boy
Mar 2, 2010

THE HORROR
THE HORROR





ante posted:

I like to lock vice grips onto connectors to give them some weight, and then hit the pins with a hot air gun with heat and airflow turned way up. They'll soften and the connector will just fall off.


Make sure they're covered in lead solder, too, not tin

I do this too but in much dumber ways that generally involve burning my fingers

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Stack Machine
Mar 6, 2016

I can see through time!


Fun Shoe

So I know you already have a temperature-controlled iron, but I know I've said this a few times about temperature-controlled irons:

Stack Machine posted:

The closed-loop control means you get an effectively very high thermal conductivity to wherever the temperature sensor is even though the actual iron can be very small.

and I want to belabor the point because I think it's a neat thing at the intersection of circuit and thermal design.

Heat flow can be and usually is (at least by EEs and HVAC people) modeled with a circuit analogy. It turns out the equations are the same if you substitute temperatures for voltages, heat flux (as in the amount of thermal energy flowing from one place to another per unit time, measured in watts) for currents, heat capacity (joules of heat energy added to an object per one degree temperature rise) for capacitance, and thermal conductance/resistance (watts of heat transfer per degree temperature difference between two objects) for electrical conductance/resistance.

So something like a flame or a 25W resistive heating element with no feedback that just dumps a constant amount of energy as heat is the thermal equivalent of a current source. Looking at the specific example of a 25W radio shack special, it dumps that 25W into the body of the iron, which has some thermal conductivity. That body is entirely metal and has some convection/radiation to the ambient environment. We can draw that as a circuit diagram with the ambient temperature as ground (so temperatures are all in degrees above ambient):



I didn't draw any capacitors here because I'm only talking about the steady-state behavior right now. We can take the Thevenin equivalent and imagine the iron as a "temperature source" at the temperature the iron goes to when it's left just dangling in the air, with a series thermal resistance Riron||Rambient + Rtip.

On the other hand, the temperature-controlled iron has a controller to adjust the amount of power being dissipated in the heating element to be (at steady-state, in some sense) proportional to the difference between that temperature and a set point. It's a thermal transconductance! (This remains true for hysteretic-style thermostats too if we conveniently ignore the behavior at the range of temperatures between the turn-on temperature and the turn-off temperature.)



The entire transconductance, Riron, and Rambient could just be redrawn as a unity gain op-amp buffer between the virtual Tset source and Rtip. The output resistance of this op-amp is Riron||Rambient, but we get to divide that by the open-loop temperature gain Gm(Riron+Rambient) to get our closed-loop output resistance at the sensor, which we can assume to be very large by design, so effectively we have an ideal temperature source at the temperature sensor location and Teff is the set temperature and Reff is just Rtip.

I bring this up because this kind of control theory application is just everywhere in basically every human endeavor and this whole "low impedance to the sensor location" thing just comes up again and again, where "impedance" can be anything from resistance to reactance (including ones you don't want like the Miller effect) to thermal resistance to spring constant (I bet the arms on a hard drive are pretty springy but the "sensor" is the servo track on the disk read by the head itself so the whole actuator system is effectively very stiff at that point).

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