Blog - All Comments

RE: 7 reasons why I like the ATmega128Dx MCUs

bit.arnab — Tue, 09 Sep 2025 09:48:22 GMT

These newer AVRs are way better than classic AVRs. They have multiple UARTs, I2C etc. and library of one peripheral can be used on other chips as well. Code portability is great. I design my projects on these only. The newer tinAVRs like t807 or t817 etc are absolutely great. The entire ecosystem is being built like you code for one and port the code for other IC just based on your requirement. I wrote a uart lib for m807 and that worked seamlessly with t807 as well

RE: Picking aluminum polymer electrolytic capacitors for the C64

bedfellow — Sat, 06 Sep 2025 16:04:44 GMT

If like me you replace the electrolytic capacitors on a 250407 C64 board with polymer electrolytic capacitors and you you use a modern switched mode power supply, you may notice a high pitched noise on the audio output. In my case I found it was due to replacing either C34, C62 or both (Vcc and Vdd supplies to SID chip). Swapping them back to traditional electrolytic capacitors eliminated this noise for me.

RE: Making an Analog Discovery 3 prop to "tear down."

DAB — Thu, 27 Jul 2023 20:02:16 GMT

I detect a level of frustration relief in that comment.

RE: Making an Analog Discovery 3 prop to "tear down."

shabaz — Wed, 26 Jul 2023 16:40:41 GMT

: ) I love that line from Contact too. Awesome movie. Lots of firms always sell double for redundancy!

Looking forward to watching the WbW video.

RE: Measuring an aluminum electrolytic capacitor's ESR

mszil — Wed, 24 May 2023 06:04:55 GMT

I came across this when trying to decide if some ancient 4700uF/63V caps are still good, and decided to tweak it for the tools on hand. I used a portable digital scope, a power supply, and power resistors. It worked quite well so I thought it might be of use to someone else with a similar setup:

First make sure the capacitors are safe (google how electrolytics heal for more info), along with safety considerations for the voltages you're working at - I kept mine in a box as a precaution. Also start with lower voltages and check the general discharge curve shape to make sure your capacitor is still in reasonable shape before trying to measure ESR.

I charged my caps to 60V thru 510Ohms with the resistor on the positive end (negative connected directly to power supply). I chose a 12Ohm power resistor (60V/12Ohm=5A peak). If possible, check ripple current limits on your caps - don't go crazy - but bigger currents increase the ESR signal and should give you some indication of capacitor condition and a few discharges at or somewhat above the service limits shouldn't cause trouble.

Next set up the scope (be careful: consider what is grounded and avoid shorting the probe ground/shield). Connect the scope probe shield to the power supply positive output, and the tip to the capacitor positive voltage - it should read ~ 0V once charged. Next setup the scope to capture a single pass, falling slope - say 200mV, 200uS/div - trigger level around -1 to -2V.

Connect one end of the power resistor to the negative supply (so the resistor, the power supply and the capacitor negative terminals are all connected throughout).

Leave the power supply running and disconnect the cap from its charging resistor and connect it to the other end of the power resistor - discharging the cap - you may get a small spark.

The scope should capture the start of the discharge curve and you should see a well pronounced, near vertical step down at the start, followed by the normal discharge slope. That correlates to ESR. In my case it was about 400mV - divided by the initial 5A discharge current = 0.08Ohm. You can repeat easy enough and play with the scope settings to improve accuracy. Wiring also matters: minimize high currents in the voltage measurement circuit, ideally use 2 sets of connections on the cap, one set to the power resistor and separate connections to the probe tip and power supply negative.

Overall it worked pretty well the first time and wasn't too hard to setup - and the caps look pretty good too. Hope it's pretty clear.

RE: Bald Engineer’s Oscilloscope Videos

shabaz — Wed, 01 Mar 2023 01:11:58 GMT

Great set of videos! Bookmarked.

RE: Bald Engineer’s Oscilloscope Videos

DAB — Tue, 28 Feb 2023 19:20:15 GMT

You have done a great job of trying to demystify the oscilloscope.

Even an old dog like me has learned new tricks.

RE: Bald Engineer’s Oscilloscope Videos

dougw — Tue, 28 Feb 2023 16:00:11 GMT

Nice collection. Did you cover aliasing in one of the videos?

RE: Selecting electrolytic capacitor replacements (for a TRS-80 Model 100) [Full Video]

javagoza — Tue, 28 Feb 2023 11:47:59 GMT

Thanks for sharing your practices. It is the part that I like least about electronics. This task has many improvement opportunities. I would like to see a chatgpt type tool that could help you in that task, it would be a great improvement.

RE: Selecting electrolytic capacitor replacements (for a TRS-80 Model 100) [Full Video]

baldengineer — Tue, 28 Feb 2023 03:29:48 GMT

While putting together a different post, I realized this one was still sitting in my unpublished queue! This video is the follow-up to the "electrolytic replacement" video.

It contains the (almost) full session of selecting replacement electrolytic capacitors for the TRS-80 Model 100.

RE: Op Amp Proto Board (SOIC-8)

DAB — Thu, 26 Jan 2023 19:15:26 GMT

Nice build.

RE: Op Amp Proto Board (SOIC-8)

wolfgangfriedrich — Thu, 26 Jan 2023 01:09:03 GMT

From the top the board looks almost home etched (minus the silkscreen) or from good old Alberta Printed Circuits.

But what layer are the big pale rectangles? Oh, maybe bottom layer silkscreen...

RE: Op Amp Proto Board (SOIC-8)

shabaz — Wed, 25 Jan 2023 18:51:45 GMT

"the PCB fab I used can, apparently, print silk directly on HASL"

That used to be quite common : ) unfortunately it's one of the minor things that the low-cost China prototype PCB services don't seem to support.

Sometimes it is handy (especially for prototying boards as you're doing, or for RF boards, or for where you've got lots of heatsinking going on, and you might want the occasional bit of silkscreen when there's no mask layer).

RE: Automated bode plot with a Pi 400, SCPI, and Python

strb — Wed, 30 Nov 2022 20:40:14 GMT

Nice! "The intern" will have to work hard to keep its job [emoticon:0f36700dfeb3494fa10d47dd9e1f90a1]

RE: I need your ideas on how to test flux!

indeterminatus — Wed, 27 Jul 2022 21:30:59 GMT

I would be interested in a fourth comparison: solder with flux core.

If it makes any difference at all, what about health hazards? Are all fumes somewhat equally bad?

Is one type of flux more "forgiving" towards beginner errors than another? (Say, accidentally applied too much flux)

What would happen (over time) if flux residue is not properly cleaned? No idea how to simulate/show that, though, unfortunately.