Re-designed My Electronics Workbench

Ever made something and you have to say later “Nhaa this isn't it”. Well I did.

I build my workbench with a double socket outlet, two linear power supplies, a component tester and a mini oscilloscope.

Why didn't it work for me:

1. Not enough light
2. Component tester and oscilloscope didn't work together😕
3. display of the mini oscilloscope was to small 🧐
4. Linear power supplies under powered (just 1 amp)🤬
5. Two linear supplies 🤪 what was I thinking.
6. Main switch off, soldering station still on 🤯
7. No fuses... 😱 I must have had a brain melt back then
8. It just didn't look nice, It looked if I had it thrown in from a distance

So I took everything out and started over.

This time I made a plan. First-up, wish-list! What do I really want:

1. With the main switch off, everything must go off
2. More light
3. Fuses... Yes
4. 1 variable power supply 0-30V 4A
5. 1 fixed (powerful) power supply with the most used voltages.
6. A bigger display on the oscilloscope
7. A hot air soldering station
8. I would like to start working with Nixie tubes, so a high voltage power supply would be handy
9. I really like my Component tester, I used it a lot. That will come back (I think)
10. Work with the materials I have, buy as little as possible
11. Make it look nice

Items from my previous workbench:

1 PC double pole switch with indicating light

1 PC double socket outlet

1 PC net transformer with auxiliary supply

2 PC panel meter for volt and current indication (max 50Vdc & 8A)

2 PC circuit boards for the linear supplies

3 PC potentiometers with knobs

1 PC circuit board with Arduino Nano and LCD display (2 rows 16 characters) of my component tester

1 PC circuit board with Arduino Nano and 1,3" Oled display of my oscilloscope

Several types of banana plugs

Items from my 'stock':

1 PC double pole switch with indicating light

2 PC single pole switch with indicating light

1 PC terminal strip with soldering lips

1 PC old ATX computer supply

2 PC led lighting fixtures with conversion circuit board and switches

1 PC net transformer 230/24+8V (90 + 10VA)

10 PC Fuse holders

1 PC Linear power supply 0-30V max 4 A

1 PC Large piece of white PVC strip (98x14cm)

Several small push buttons

Several types of banana plugs

Various electronic components like (transistors, mosfets, resistors, etcetera)

Several colors of PLA wire

Items to buy:

1 PC panel meter capable of measuring at least 300Vdc

1 PC 2,42” Yellow monochrome Oled display

1 PC single socket outlet

1 PC Hot air soldering torch

Warning! We are going to work with a net supply (in my case 230V 50Hz).

Work safely, that means for this build, unplugged from the main source!

This is the “Main distribution panel” of my workbench.

I made a small sketch of the Main electric system. (see P300.pdf)

I wanted the main switch, the switches of the variable power supplies and switches for the lighting all in one place together with fuses, also the fuses for the additional power socket, soldering stations and fixed power supply. To make it look nice, place everything in a panel and connect it to a terminal strip.

What I didn't have back then, but do own now, is a 3D printer. So I designed in thinker CAD a panel.

Note: the words on the panel are Dutch.

I had ordered once two desk lights with loops, but their bases were broken during transportation. The company who send them didn't want them back. So I took them apart, kept the power converter print, switch and lighting fixture and thrown away the rest

I have mounted the lighting fixture on either side on the top shelf of my bench and mounted the print on the inside of the desk

I used the large PVC strip as my front panel, it just happens to fit nicely between my top shelf and desk.

Made holes in it for my 'main panel' and double socket outlet. Placed the terminal strip inside and mounted a copper strip for the earthing. To connect it to the main source (a socket outlet in the room where my desk is placed)I used a cable with a plug and connected it to the terminal- & earthing strip.

(note: make sure you have a strain relief on your cable)

I have a very decent variable power supply, made almost 30 years ago by a friend. (forgot to make a picture 😒) Old school meters in it, and heavy! The switch started to show its age, it didn't work as well any more. So I decided to build it in my desk and dump the switch (I use the new one now in the main panel).

The old transformer (230/27V) was way to big to fit inside the available space, it was a whopping 320VA transformer. An overkill for the max current of 4 amps the print was designed for. So I used an old transformer(230/2x27V) from a radio of 120VA

The plus side of this transformer was that it had a net filter and an auxiliary supply and it fitted inside the available space.

Made new wires on the print and attached them to a terminal strip and placed it on the “ceiling” of the place where the transformer also was. The space is limited! The cool rib with the rectifier bridge and the two 2N3055 transistors are placed on the back of the desk, drilled a hole through the back and connected it to the terminal strip. I also dumped the two old analog meters and re-used on of the Digital meters of the previous variable power supplies. Here the auxiliary supply of the radio transformer came in handy it powers now the new display (see also P304.PDF)

The whole system works around 2N3055 transistors and a LM723. See also the basic schematic.

Some of the resistor values on my print are a little bit different to get a real 0-30V output, but this is the general idea. It is an old, but reliable design.

Tinker time!! 🥳 designed a new panel for it and placed it in the white front panel, hooked it up, and it is running purrrfectly (yes, I am a cat person)

Before you ask, no the colors aren't random! Red is danger, yellow is warning and I will make some green (safe) ones to.

The easiest way to get a fixed power supply is to use an old ATX computer supply.

They are widely available, and I just had one lying around.

It gives a +5V (Stand-By) even if it isn't switched on.

Switched on it gives an even more powerful +5V but also +3,3V, +12V and a -12V. Since this are the most used voltages, it is a handy tool to use.

Personally I don't like the messy wires, so I took the supply apart, de-soldered the original power wires and replaced them with 1.5 mm² wires. For the control wires, I used 0.22mm² wires. See here some picture's connection info.

I am not going to say too much about it, there are dozens of builds to find on the web and here on Instructables. Check them out and/or check the schematics I added.

Just make sure you have plenty of airflow.

The only thing I did extra was to add female USB ports in the front panel on the stand-by supply.

With this one I can't warn you enough!

Do not connect this straight on the Mains supply, use a decoupling transformer!!

This is a dangerous voltage, it contracts your mussels!!

!!!DO NOT USE IT, IF YOU DO NOT KNOW THE DANGERS!!!

But if you really want to build it, this is how I did it.

It is a fairly simple design, a rectifier with a capacitor (please check if it can handle the peak voltages), a mosfet (IRF740) controlled by a pot-meter and a BC547, 12V zenerdiode, 3,3Ohm resistor as a current limiter circuit. It is not stabilized, I just want to use it for testing Nixie tubes. Perhaps I come back on this one, but for now... this is it!

I couldn't find the right transformer. Ideally, I would need a 220Vin/220Vout transformer. So I did the next best thing, I used two transformers with the same characteristics. 230/5V removed from old telephone chargers. Unfortunately this meant some losses, I eventually ended up with 197Vac which came, after rectifying it, just shy above 250Vdc. But I can live with that 😜.

I had bought a digital voltmeter that could measure up to 500V, but needed an external supply.

Guess what 🥰 I just love old phone chargers. It provided just that.

I do not care about the current, it just can give about 100mA (still dangerous!!)

Placed the meter with the potmeter in a nice panel with some safety banana plugs. Job done.

This-one was originally from Peter Balch (https://www.instructables.com/Oscilloscope-in-a-Matchbox-Arduino/) it was nice to build, and it really works well. If you would hold in your hand, like it was originally planned, then the display is OK, but build in a panel means that it has a lager distance from your eyes than if it was hand-held. It was really hard to read-out. So a bigger display was needed.

My initial idea was, to simply replace the existing 1,3”Oled I2C with the new 2,42”Oled I2C/SPI. Just set the new display to I2C with the switch on the back, adapt some code and we're good to go.

If life was so easy!

The whole system just froze-up. After some analysis it turned out that the new library for the new display was rather large, and it pushed the Arduino Nano to its limits (over it actually).

So why not use an TFT display, you may ask. Well, they work differently than Oled displays. If you activate a pixel(s) on an Oled, it turns off when that signal isn't repeated or disappears. That is not the case with TFT displays, here you have to actively turn off the pixel(s) because the on-board driver keeps repeating it. That is a lot harder to program.

To be honest, I used the digital inputs more instead of the analog. I work more with digital electronics than analog. So skip the analog signals.

Nope, still no go.

Then it hit me, I was approaching this wrong. The software from Peter was based on an analog system, even the digital signals were treated as analog signals. What if I treat them for what they are, digital signals! Just read them in as boolean signals in an array en only adjust the sampling time and plot them in one go. This would simplify the program a lot.

To a certain level I understand Code, I can adjust Code, I even can write simple programs myself. But this was another level of coding, so I called in some help from my good friend ChatGPT 😁.

A fair warning! If you can't code at all, ChatGPT is not going to help. It makes small mistakes (like it kept insisting that the display address was 0x3C instead of 0x3D as the manual said)

So you have to be able to read the code and make small adjustments to make it work.

But in the end I got a nice compact little program and it works great. Except for 1 thing. Normally, I use the parameter INPUT_PULLUP or INPUT_PULLDOWN when defining an input, but that can't be used with an array. So I had to add Pull down resistors on those channels in order to prevent false signals.

See also P310.PDF I have added

But this isn't an oscilloscope anymore, this is a digital analyzer!

I designed a new panel. Due to the fact that the mounting lugs for this display are on the back, I had also designed a pair of brackets that I could glue on the back of the panel. A few screws in it (🤬 they weren't metric), and it was finished.

For my regular soldering station, I simply added a socket outlet on the back of my desk and hooked it up to the main panel. And Bob is your uncle!

For the hot air soldering station, I got inspired by Dinconnu build of a hot air soldering station https://www.instructables.com/Cheap-Hot-Air-Station-With-Arduino/

He built it with the stuff he had, and so will I.

I bought just like him a handle, and checked the wiring, the colors were different. So if you also want to build this, always check the wiring!

For the 230V control, I use a S202SE2 I had in stock. It combines the Triac with an optocoupler, all in one housing. For the fan control, I used an IRFZ44. And let it control by the Arduino as well

I reused the 1,3 Oled display from the oscilloscope, and bought an MAX6675.

For controls, I used 4 push buttons, two for speed up/down and two for heat up/down

To connect the handle to the electronics, I used a sub-D9 socket and plug, the (female) socket in the panel and the (male) plug on the cord of the handle.

See also the added schematics

There was a din12 female socket on the cord, I removed it:

1. I don't like touchable pins with life net power on it
2. I didn't have the opposite socket
3. I like to remove it to create space

But number 1 was the main reason to do it so

The only thing left to do is design a holder with a magnet to turn off the heat when it is in the holder.

But other than that, 1 hot air soldering station done and dusted.

My initial thought was to re-use my component tester, but I also what to be able to test logic IC's. I have a bunch of them!

Sins I only have space left for 1 item, I have to combine them. That still a work in progress, I figure I write a separate instructables on that one.

I did add additional earthing banana plugs to earth metal casings while I work on them. Seemed like a good idea. And created a label for them 😁 just to be clear.

And here you have it, the (temporarily 🤪) final result

Final words

I hope I can inspire someone to adjust their workbench to their needs, with the items they have in their own stock.

Fore those who want to use my front-plates and adapt them to their own needs, here is the link to Tinkercad.

https://www.tinkercad.com/things/fQkDJtAOO0Q-testbank-frontplaten-en-steunen?sharecode=BHezkHMzpQEh5B0st_IxdwIXBirXWHwP_yOq0U4GKWM