2014. szeptember 30., kedd

Engineer joke

A Fluke (Philips) PM3382 oscilloscope fall into my hands. It not really works.
At power on I got this error message:

If you can't read the text (none of the handles works, so I can't arrange the focus) here it is:


Funny guys.


Here are already wrote, that I'm in trouble regarding multimeters. If somebody want to measure electronics correctly, unfortunately one multimeter is not enough.
It is frequently required to measure various parameters in parallel. For example if you want to measure the efficiency of a power supply (what I'm playing with this days), you need four multimeters (input and output voltage and current).
The take-of point was two multimeters. An old Metex and a Chinese crap called Maxwell what I bought a few years ago.
About the same time both of it died. The Maxwell done various things, went to the trash. The Metex stopped to measure resistance correctly (I don't want to trow it away, but I don't want to use it either).
To overcome the "multimeterles" state of mine, quickly bought an Agilent (ooops, it is Keysight now) U1232A to have at least one decent meter. On top of this I bought a Sanwa PS8a. This goes into my bag, because it is not really usable on the bench. You can't even put crocodile clips on it.
So it still leave me with one DMM.
I wanted to acquire the others cheaply. Ordered 3 (just two for myself) Uni-T UT136B. This looks like a decent one even it is Chinese. And in addition ordered a HP 3478A (used cheaply) to have a reference device.
The first package lost - I still in conversation with the seller. The second one was in the hands of the Hungarian customs and the UPS for two weeks. When it finally arrived (two weeks ago), my colleague realized this is a 120V version, so I will have some work with it before I can use it.
Finally I still have only one multimeter.
Update - yesterday I got a Fluke 117 bought cheaply on ebay.

2014. szeptember 29., hétfő

Kapton transfer - FAILED

Base on this article I also wanted to try out the Kapton tape instead of the paper I'm using.
The result....

First of all I was thinking, that the whole thing is a catastrophe and goes to the trash.
After it I was thinking over my past and realized the following:

  • The photo resistive process was never working to me.
  • The toner transfer I'm using today started to produce acceptable result after months

Compared to these the Kapton based solution is not to bad even.
What I know for sure:
  • This board will be created with the regular paper based transfer
  • I don't give up this Kapton based process, I will continuously trying it.

The Little Box Challenge

After long thinking, team building, I couldn't resist. Registered.
Don't be afraid. The real work will not come from me. I'm just "managing" the team.

2014. szeptember 19., péntek

POM #1 - Voltage inverter for breadboards 2.

After some fighting (with myself) finally ordered the PCBs.
The dritypcbs immediately create this view from the gerber what is awesome, I'm fell in love. :-)

Yes, you can see it correctly, not just the POM1 on the board. On the whole 7 PCBs on the board. 4 POM1 and 3 PCBs what allows to use various connectors on the breadboard: Stereo RCA, USB B and 3,5 mm jack.

2014. szeptember 13., szombat

POM #1 - Voltage inverter for brreadboards 1.

I was thinking a lot, how to start this series, to finish the design by end of the month for sure. Among the project in my head this is the simpliest one.
The job of this thing to invert the voltage (typically +5V) arriving to the breadboard, generating a -5V loadable with a few mA-s.
What this is good for? Frequently happening that I need analog circuitry - typically opamps - connected to my digital stuff. In addition, the single supply is not always enough for these (handling DC coupled analog input signal).
The circuit is built around the ICL7660 (LTC1044, LTC1046) and contains only two external components - two 10uF capacitors.
The design is finished. Even I tried it out.
Schematic design:
Built (On breadboard):

The picture requires some explanation. The DMM measures the voltage between incoming ~5VDC from USB and the output of the ICL7660. It would be good to show more values but unfortunately in this very moment I'm not really equipped with multimeters.

PCB design:

Cost structure:

The full material cost is around 2€, what doesn't look to much. In this time I'm intend to try out the Dirt Cheap PCB as manufacturer.