Putting some bench grinder wheels under the microscope, here is a selection. I may update this post as I get new ones or also add some older/used ones I have sitting around.
Picture Grit Type Manufacturer 36 NK Manufacturer 1 36 NK Manufacturer 2 60 NK Manufacturer 1 60 NK Manufacturer 2 60 EK Manufacturer 1 80 SC Manufacturer 1 80 SC Manufacturer 3
100μA and 50μA Reference
I recently built this small microampere reference using two LM334 current references. It is powered from a small 3V lithium button cell.
HP 3478a Standby Power Supply
A while ago I replaced the battery in my HP 3478a multimeter, this battery is in charge of keeping the calibration values inside an SRAM. Since I norally have the multimeter plugged into the wall anyhow I decided it may be a good idea to add a standby power supply such that the battery doesn’t drain that much (other than its internal resistance).
So I did. There is a 78L05M generating a 5V rail, and I also added some super capacitors for good measure that on their own will keep the SRAM supplied for >1 week without the battery. The transformer is short circuit safe.
Zoo Saarbrücken January 2023
All pictures taken with my Sony SLT-a77 with a Tamron SP AF 70-300 F/4-5.6 Di VC USD objective.
Corsac Fox Snowy Owl Eland Antelope Zebra Peafowl Penguins Cheetah Flamingos
Winter Impressions January 2023
All pictures taken with my Sony SLT-a77 with a Tamron SP AF 70-300 F/4-5.6 Di VC USD objective.
Förderturm Itzenplitzer Weiher
Halogen Lamp Driver
Just a quick and small project, I put an electronic transformer into an enclosure. It’s my favorite EuroBox enclosure, front and backpanel were 3D printed.
Update 20.01.2023 I replaced the lamp driver with an old 12V halogen transformer I had sitting around. For further protection I added a polyfuse to the secondary side.
La Gravière du Fort 10.09.2022
Was quite cloudy and cold, water temperature at -10m was still 23℃ though.
All of the following pictures were taken with a GoPro 7.
Smoking VEB Statron 3224
During full load some resistors on my VEB Statron 3224 started to smoke, so let’s investigate. The power supply is a fairly simple construction using a LM723 and a large pass transistor.
The first two resistors are for clipping the maximum current on the 8.5V (4A) range. It’s the two large resistors at the top left of the ciruit board.
The two resistors are 2R7 and 0R82 in parallel, giving an equivalent resistance of 0R62. My electronics supplier had no resistors with >5W in those two sizes, but I can arbitrarily chose an alternative as long as the equivalent resistance is close to the 0R62. My first thought was 1R2 resistors but my supplier also did not had these in stock. I replaced them with two 1R5 which nominally give 0R75 but in this case actually measures 0R68 (with kelvin leads). The current now gets clipped to 3.92A which is fine by me.
La Gravière du Fort 27.08.2022
All pictures taken with a GoPro 7.
HP 3478a Capacitor and Battery replacement
Replacing the old RIFA capacitors Older RIFA capacitors are known to crack, which results in moisture getting into them which subsequently lowers the internal insulation resistance which at some point results in catastrophic failure. I had a couple of those explode on me in the past.
On the HP 3478a the RIFA capacitors are mounted before the mains switch meaning that they are live whenever the multimeter is plugged in. Which means that unless those have been replaced I would not leave the meter plugged in without supervision.