Friday, May 25, 2012

Velleman K8055 - light sensors

I want to use the Velleman K8055 for data collection and also for remote control, so I started testing the analog inputs for sensor.
The first pair of sensor (will multiplex the inputs for others) is to get light conditions, will put a south faced solar power meter and a light above intensity meter. The relation between both during the day will, I hope, give me rough idea of the sky conditions.
 For the light above intensity meter, the idea is to have a small tube pointing up with an LDR in the lower part. Since the K8055 analog inputs basically measure voltage I used an voltage divider, series of the LDR and a fixed resistor. For the South faced solar power meter nothing simpler than a small solar cell, I used two to compensate losses in the cable (will be a long cable run and the cells output very low power). Across the cells there will be a resistor for direct power measurement.

For fun, I run some simple math on the power from the solar cells and if scaled I would got 100W by each square meter (had no ruler by hand to measure the little cells so it was a ball part guess), the panels represent 0.00024 m2 and considering a 500W of total solar power during daylight hours that would give me a 20% in efficiency... a plausible figure considering the inaccurate data.....

Other sensors will follow, maybe next will be temperature.

Wednesday, May 23, 2012

Crystal penning

As referred in the previous post I was building a circuit with a Polyakov mixer, for that circuit I would need at least two crystals; 3920 and 4144 or 7840 and 8288 Mhz (double of the first values). Unfortunately when finding odd crystals their never in the junk box, so I remembered a page I have seen before on the subject of crystal penning, by Hans Summers.

The idea is to open the Crystal case and start "writing" on the crystal itself to lower it's natural frequency or as others have done start grinding the crystal to raise the frequency.

Opening the crystal case it's the hardest part because one has to have a little care, luckily for me I opened 3 of then with an hack saw and none got broke, expect the first one that got a little bit loose from the support but never the less it works.... the best technic IMHO is to cut first the thin (top's) part of the crystal case (both) and then gently start cutting the biggest parts until some holes start to appear, then slowly break the remaining metal. I took me about 3 minutes for each crystal, using a vice for support.

For the penning itself (I didn't tried grinding since my wanted frequency was lower) I used an "Edding 3000" pen like the ones used to make printed circuit boards, and just "wrote" on top of the crystal, sometimes it stooped working and it was time to let the ink dry. I also tried with nails varnish but had to clean part of it so the crystal would resuscitate, I guess nail's varnish is too thick for the job.

Now, here are my experiments: 

The one in the crystal tester is completely painted in black..

The 4 Mhz crystal, got to this:

I need 3920...

The 8Mhz version, almost 40Khz...:

I need 7840...

The 8.365Mhz crystal:

..close but not there to 8288 Mhz

....didn't managed to get further down on frequency, the crystals would stop working or maintain their frequency because the ink would not deposited any more, the pen would dissolve and clean the previous ink I will continue my search for the mentioned crystals, or build a PLL... :)

Anyhow it was fun!

Sunday, May 20, 2012

Velleman K8055

This Saturday I was at the shack experimenting with a 74HC4060 as oscillator/freq. divider and a Polyakov mixer (more references to this on a latter post) and looked at a box containing 2 un-built Velleman K8055 kits....., since the Polyakov mixer was working (different from working at full performance), why not change a little bit and build one of the kits...
I have the kits since 2005 and the PCB board was printed in 2003.... originally it was to make a control box to remotely hard reboot computers in a data center but the project never went of.

Now the idea for the kit is to put connected to a low power PC running 24/24 switching different audio inputs from different receivers and also recording of environment values, like temperature, energy, wind speed, etc....

The built time was less than an hour and the instructions were not read :), just soldering directly from the component me I know what I do...

After installing the Linux version of the K8055 lib and utilities from here, time to configure and test, I was nervous since it was built in a hurry...

The only "issue" I had was with software in the usb hotplug in Fedora 6, the  usermap file is placed in /etc/hotplug and the k8055 file stays in a sub dir of name k8055, just a little different from the instructions but normal stuff due to distributions differences...

On to the real test, let's put a binary output of 224, analog #1 with 224 and analog #2 with 16:

The command is: k8055 -p:2 -d:224 -a2:224 -a1:16

my board I configured with address #2 (-p:2)

Here's the result:

So the left most led is the power indicator then at right the top most is the analog output with value of 224, bellow dimmer is the output #2 with value of 16 and then the binary for 224 (MSB on top)...
Inputs are on the left side of the board, reading also worked nice! the "pain" part will be outside world connection and boxing of the board.

I am parting with the other kit, it's un-built and complet. I'm asking the value of 33.32 Eur that it cost'd me in April 2005 (still have the invoice) or the equivalent value in Amidon toroid cores :) you prefer an exchange...

Have a nice week!

Saturday, May 19, 2012

Wooden dipole support

I promised a friend a simple HF receiving antenna (while he doesn't decide on getting an ham license) so I just made a simple wooden dipole support, wires will be cut for the 20m band since that's just fit to the space he has.

It was varnished so it would last more in rainy days.
The 50 Ohm cable will be supported looping on the support groove in the middle.
The bypassing hole in the middle is just if we need to hang the antenna at mid point, my dipole has a similar design an the wire used can easily support the transmission line weight, I use cooper covered steel wire.

The support it's a little bigger than needed so the eye bolts would not touch each other midway, a shorter version could be made with just holes in the wood for the wire support but this way just look's nicer...

Have a nice weekend!

Wednesday, May 16, 2012

HF antenna tuner

 This box is laying in the shack for so long that I almost had forgotten it.
At some point I had an FC-102 antenna tuner that worked great on my "piece of aluminum tube" vertical antenna, then I decide to part with it because I didn't had the matching FT-102 transceiver and I could easily built another antenna tuner. I regret that decision, I have now the FT-102 but not the FC-102....

The swr meter built in the box is a Daiwa cross needle and the rf caption is of the bridge type. works nice.

The variable caps were an ofter from a friend, although not in perfect state they do work, I will improve the shaft electrical connection to the vanes, it's a little loose and I don't want intermittent operation. The coil was bought at some hamfest thinking in this build.

Mechanical work is just a pain if you don't have patient and shop full of  materials.
 The shaft isolator/coupler is just a little piece of plastic hose, not the best solution but for now it's enough.

Schematic is a simple T-match, the coil connections were made by testing, for each band, with the antenna analyzer, for best match but the coil material is not easy to solder so I will probably replace it, see last image. I added a parallel 56pF cap to left tuning cap to extend range, In the future will put a switch in and out of circuit.

It can match my 18Mhz band dipole to any band between 1.8Mhz and 29Mhz.

Now I am building a new coil to replace the present one. Just need to get some wire....

Of course the can will be's just a fixture for the coil winging.

Have fun!

Friday, May 11, 2012

In the oven

Since the Swan 270 already left to a good an caring home (I hope) I didn't recovered the variable capacitors but I had in the junk 2 that had to be a little cleaned and greased... let's hope the next few days I can prove they are able to work some more years in this assembly:

I already made a preliminary test without full success (eg: have to work on pair with an equivalent part from a know manufacturer), anyhow was latte and was just a simple test, hope the next few days can put this to work. Shouldn't be difficult hum?!

Tuesday, May 08, 2012

Goodies from Lisbon

Had to go today to Lisbon today and since I had some spare time, decide go to an electronic shop that I used to go when I worked at the country capital...
I just took a small list because now I'm in reuse mode, I wanted an NE604 an MC1350 and a BPW34. Well I came with the BPW34 photo-diode, 3 LDR's and 2 on/off switches. The NE604 and MC1350 were to specific, I guess, for them to stock.

 The NE604 was just to make some tests, the MC1350 was to have one spare and the BPW34 is to make more "light comunication" tests. The LDR's were a last minute impulse buy and will probably be used for more one, D.O.S.I. (department of stupid ideas) type, posts.

Meanwhile got this on an email from a ham friend.
The boys at 706T might need one....

I would for sure loved to have one!

Have fun!