2018. január 7., vasárnap

VESA Monitor Stand

I've a Philips monitor in my lab. Unfortunately together with it's original stand it is to high. This means I can't really access the shelve behind it. I needed to place it lower, but it's original stand doesn't allow it. Yes I know, that I can buy a monitor with adjustable stand, but it cost more, and actually I've this monitor on-hand.
So I designed and built a new one.

The original status:


The stand design:

(The gray parts are aluminum extrusions)

The parts:

Yes you see correctly. It is a weight used for exercise in the gym. :-D

Assembled:

The monitor built on it:

In it's place:

Now I can use that shelve.
The files are published here: https://www.thingiverse.com/thing:2749210

2017. december 25., hétfő

Spiders in the corners

Sources on the Thingiverse

The big heights in the house looks great, but it has a dark side. The spiders in the upper corners. It is not easy to remove spider nets from 5m height. Either you need a big expandable ladder (what I hate) or something expand your arm to such length.
I chosen the second option.
Bought three 2m length aluminum pipes, 30, 25 and 20mm diameter, and designed this:


Printed it in four versions. Two pieces in one set:


Assembled (one set: eight M4x45 screws, eight M4 nuts, one M6 nut, one M6x15 thumbscrew):


How does it look like when expanded:


Let's tremble spiders! I'm coming!

2017. december 19., kedd

Printing for my Lab 2. - Hammer holders

Continued to populate my pegboards. Now I made something for my hammers:


Printed and assembled:


Hammers mounted:


2017. december 12., kedd

Printing for my Lab

After a long time (I think around 3 years) I decided to reanimate my CNC Router.
As first thing I cleaned the mess on its top (mainly the new stepper drivers, elastic couplers, drill and mill bits was there). I wanted to have final place for those drill/mill bits. So I printed holders for it, what can fit on the tool holder board:

Designed:

Printed:

In work:


2017. december 10., vasárnap

High Voltage DC Power Supply 4. - The phase switching module

!!!DANGER!!!
The circuit described bellow is dangerous. Using it improperly will kill you. On the other side I may also made mistakes during the design and built. I'll take absolutely no responsibility for it. If you want to build it, please don't ask for circuit board or help. I won't help you.

In my previous posts about the high voltage supply I already wrote about the small electronics able to keep the GND of the DC side on earth potential without isolation.
No this is not voodoo. It just a simple circuit.
The theory:
The protective earth connection in the mains connector is connected to the mains null somewhere in your system. Probably somewhere around the utility meter. So if we measure the voltage between the Line and Earth, it will be the full mains voltage. If we measure the voltage between the Null and the Earth, it will be zero. To be able to work with, I draw the following circuit:


This is just two simple zener regulator, what provide the necessary sense signals for the further processing.
I designed a complete circuit around this, with an MCU, a 5V power supply, MOSFETs for driving relays and two DPDT relay.


The board design:



Based on this design I ordered the boards from allpcb. Actually I made a mistake around the design. I bought my relays after I sent the board for manufacturing. The result is that I connected the switched circuit on wrong direction. This means if I build the circuit the relays create a short circuit to the mains.
Throw away the boards (without even soldering a single component), ordered a new batch.
It also arrived within a few days:


The finished board:


I wrote a small arduino code to run the board. It has an ATTINY84 in it. Actually the code would fit in an ATTINY24 easily.
Assembled the whole thing into it's final place:


I connected the final thing to the mains. Switched on the power switch. Everything looked fine, until I pressed the output button.
The main circuit breaker in my house went off. Shitt.
Few more tries. The result get even worst. It killed the mains even switching on the power switch and not the output button.
Removed the phase switching board. Measured. It looked like both of the relays killed. There was a short circuit between the line and the neutral on the board.
Here is when Murphy comes into the picture. How many components buy I usually for my circuits? Way more than needed. Except this case. I had only those two relays on the board. Weekend. I should wait until Monday, to replace the relays.
In the meantime I removed the relays from the board - I hate the THT desoldering.
Removed the cap from one of the relays to be able to make a picture of the burnt contacts:



The surprise come here. No burned contact. Even I made a picture with my microscope. The result is the same:


Nothing, the contacts are intact. Measured the second desoldered relay, what still has it's cap. the result is the same, no sign of the failure anymore.
Just my guess that the heat and mechanical torture of removing the relays of the board resolved the temporal latch-up of the contacts.
Now back to the basics. As I can't find out the source of the problem (didn't wanted to play this game with new relays). I just guessed that the inrush current of the capacitors causing the problem (as I wrote earlier, I had problem with it already). So I hacked a solution. Together with the new relays I bought some inrush protector NTCs. It isn't an ideal solution, but hopefully will be sufficient. Hacked a PDU board to accommodate the NTCs. I've a few spare anyways:


The relays replaced. The whole thing works as expected.
I'm still thinking about the proper solution. The device is a tool and not a target for me. So it may not worth the effort to build a second version.

2017. december 4., hétfő

Conrad Energy Logger

I'm quite unhappy.
Yesterday I checked the thermostat I built for the dog house. I felt that is maybe some problem with it. So I wanted to check the power consumption. If it is between 30-40W means everything in order.
Here is the result:




Well done Conrad
Congratulations for this extremely reliable, stable product.

2017. december 1., péntek

My new toy

My new toy arrived. Preparing myself to build a 3D printer with large build volume.