Doorgaan naar hoofdcontent

Fun with a laser cutter part 1 (Base for a relay board)

Theo Kleijn has his laser cutter setup and it was time to make something useful.
Theo's blog :

I took a board I had laying around, a 16 relay board, similar to one found here : and

And decided to make a nice base for it, so it was not directly on the table.

I started by designing the base plate, I measured the board and made a drawing in LibreCad, which was in the Ubuntu repository.
This was not a success, when trying to save the file the program segfaulted and all my work was lost.
I already had a license for QCAD 2.2 (on which LibreCad is based) and have used it without problems on my old linux machines (in 2008 and later).
The old version I had was alright, many productive shortcut-keys etc, but many improvements were made since that time (the version is now 3.4.6) so I went to the website and purchased another license, for only 32 Euro, which is very low price for such a good program. (Thanks Andrew)

I drew the the board outline and mounting holes.
I then offset some extra space to make the outline for the base.

First I make a sketch on paper

Made a precise drawing in QCAD
I exported it to DXF and loaded the file into LaserMate (a windows program that came with the laser cutter) where we cut the part.

We also made some nice plexiglass spacers and added some text in 'scan mode'

This is the result.

Next will be a full box with cut-outs. We just need to design one.


Populaire posts van deze blog

Denon DHT T100 DESIGNED TO FAIL : bad caps (ceramic caps this time)

A friend gave me a Denon DHT-T100 to look at. Do not spend much time on it.. ok. It had a problem, it started clicking and ticking after power on, and after some time. (a so called intermittent problem) Sometimes it did not tick or click, but it was basically not usable. The clicking had a sharp click in one channel and repeated after about a second, then sound recovered and it would click and drop out again. He told me, do not spend any time on it, yeah, right. ;-) like I would give up after 15 minutes. I wanted to know what was going on with this thing, I found some schematic online and started measuring the usual things. The power supply, 24V did it drop down when a tick occurred ? Difficult to find out because sometimes the thing would play for hours without a glitch. I eventually found out the 24 V PSU, the step down SMPS on board and the LDO's were all ok, all power rails remained within spec, but it still glitched sometimes. (while power was ok) I investigat

Fixed voltage on cheap buck converter (MP1584) conversion with single 0805 resistor

Everywhere I look on the Ali and Ebays I see these step down converters based on MP1584. I bought a couple and actually they are not bad at all. The output voltage is set by the trimming-resistor in the left top corner of the picture. This works OK, but.. it is dangerous because it is rather sensitive to the touch. I decided that I wanted fixed output, so I had to figure out how this thing worked. The datasheet looks like this : R1 in the datasheet is what I call "R feedback" in my image. The value of R2 is mostly 8.2K Ohm in the boards I have seen.  So to set some common values for output voltage: change R1 to 27K for 3V3 output (actually 3.4 volt, but 27K is a standard value) or change R1 to 43K0 for 5.0 Volt output. (43 K is a standard value) A standard 0805 size resistor fits precisely, how convenient ;-). Make sure the other resistor is really 8.2K because that determines the feedback ratio. This way you can not burn up your circ

Raspberry Pi, PyFace Digital, the lost documentation, I found it finally

The Raspberry PI or R-pi from  is well known these days. It is not an accident that I have one, I have been doing Linux stuff since 1991, and professionally since 1996 I can not skip over these developments, have to keep up with the new kids. :-) Times have changed, hardware has become very affordable, everybody knows the Arduino , Raspberry Pi and Beagle-Bone-Black (BBB). Not everybody knows the stuff that  aka Acme-Systems and  aka  Olimex make, so I will endorse them here. Since I am an engineer I expect to connect switches and relays to the boards and some documentation with products, not so with the " PiFace Digital " board, it comes without serious documentation, not a even the schematic. All links on their blog point nowhere. People asked them many times, yet nowhere is the schematic to be found. I finally found some info after hours of google-work, someone made a c