Cat tweeter, order placed

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SparkFun Electronics Order

Date Packed: 07/25/2012

Shipping Method: UPS Ground

Items shipping in this package:

Breakout Board for XBee Module x1
Logic Level Converter x1
Voltage Regulator - 3.3V x1
2mm 10pin XBee Socket x4
RFID Tag - 125kHz (retail pack of 5) x2
RFID Reader ID-12 (125 kHz) x1
RFID Reader Breakout x1
XBee 1mW Chip Antenna - Series 1 (802.15.4) x2
XBee Explorer USB x1

This is for my new tweeting cat project. The plan is to hook up the RFID Reader ID-12 to the XBee Series 1, and send data to the other XBee Series one which is hooked up using the XBee Explorer USB to my playstation 2, which will send tweets based on where the cat is. I'll put the RFID tags on the various places that the cat goes (drinks, litter box, other cat, cat toy, sleeping place, doorway, food bowl, et cetera). Biggest concern are the batteries, but I'll figure out what to do with that. Most likely it will need a harness to avoid the cat being entangled in wires, and to avoid the RFID chip getting into the water bowl.

High definition digital antenna

For some time I wanted to build an antenna for my high definition television. When the AT&T U-verse system stopped working, I decided now was the time. I was subscribed to Make magazine for a while, and they had a good description of a possible antenna. I had already bought the "75 to 300 ohm matching transformer with spade clips on one end and female F connector on other" so it was just a matter to put things together. I didn't want to waste clothes hangers, and I didn't have a nice piece of wood, so I went a step cheaper by using cardboard tape and European grounding wire. I connected the wires by twisting them together with pliers. The result is visible in the picture on the left.

On this picture you can see most of the back side, including the way I twisted the wires. I used black dots to mark the places where the screws would've been on the original, as you can tell, one of the wires slipped a little bit. I hooked the transformer up using European screw blocks, of which I removed the plastic to ensure better contact. The total price of this antenna was less than $5, although I hooked it up to the television using an expensive gold plated antenna cable that was over $50.

Making sure the television understood the input was from an antenna and not from cable and to scan for all the stations was slightly tricky to figure out, but after it had discovered two channels I knew it was working. In the end it found over 60 channels, all local, of which most are Asian for some reason.

Below a picture of the television screen using the antenna. As you can see it provides a flawless 720p high definition signal from KTVU-HD. My apologies for the camera flash.

Phone charger for bicycle

The latest project I made was the USB port for my bicycle. I had the circuit ready a while back, but I hadn't moved my Nexus in-hub alternator to my new bike yet. The Google bike to work day made that easy, as they had a bicycle workshop where they were quite helpful and making the change (I couldn't do it myself due to lack of a good tool to undo the old wheel: it had been tightened a lot).

Initially my circuit had only a 10uF capacitor after the diode bridge, this turned out not to work and confuse the phone a lot. After increasing this to 230uF by adding a 220uF capacitor everything worked well, but a 470uF probably works even better.

Here you can see the circuit actually attached to the bike (using electrical tape for insulation). You can see the Nexus wheel at the bottom and the USB connector with the plug heading to the phone. As you can see there is one wire hanging loose, this is the ground wire, which is not needed as the alternator itself is already grounded to the bicycle. I prefer to leave it disconnected to avoid ground loops, although it is unlikely this will happen.

There is also a switch, shown here from the side, which allows you to turn off the circuit (which will make it easier to cycle, as there is hardly any resistance from the in-hub alternator if there is no draw) or switch the power directly to the front light of the bicycle, which was the original configuration.

The final question is whether it works, and it does. The first trip I got 2% charge (from 28% to 30%) the second trip 5% (from 90% to 95%) and the third trip 8% (from 66% to 74%). This is while the phone is operational (and actually syncing Email in the Mountain View WiFi area).

GPS for Nikon D7000 (or D90)

I recently bought a D7000, and noticed it had a GPS input. Since I already had the GPS module (see the GPS label) I was wondering if I could connect the two. It turned out to be easier than expected: the GPS module accepts 4-6V (and the D7000 outputs 5.9V) so no regulation is necessary. The GPS output is 3.3V, and my Nikon D7000 accepts that without any problems (I've read reports of other Nikons that need a higher voltage, in which case you can use the 74HCT125 as mentioned in this schematic.

The trickiest bit is finding which cables to connect, however, there are enough resources online, like this blog for the D90, that explain it rather accurately.

I put the GPS inside a mini Altoid box, and will probably use the foot that I had for my Minolta project. To activate the GPS on the camera you need to go to the GPS menu. On the LCD display you can see the status: if it is blinking it means you connected everything correctly, but the GPS hasn't locked on yet. If it is solid, it is in use. Note that the Nikon stops listening to the stream if the data isn't being used for a while, but it keeps powering the GPS (I believe even when the camera is turned off, so you may wish to unplug if you want to save the batteries).

PS2 to MIDI converter

Recently I purchased an EMT-10E (Yamaha sound extender) which was meant for the Clavinova to increase the different sounds you could make. I bought it for the project I mentioned earlier on this blog, so I would have something to hook the toy piano with MIDI to once I was done. However, due to issues with the switches the toy piano still doesn't have MIDI, and I still wanted to play with the EMT-10E. So I decided to make a PS/2 keyboard to MIDI converter. Since a PS/2 keyboard already sends key press and release commands it would be just a matter of converting the protocol and assign a note value to each key.

As this didn't seem to difficult, I decided to give myself another requirement, which was that it had to look nice. As you can see on the picture, I think I succeeded. Initially I decided to use a wood box, but the PS/2 connector that I got from Jameco was too narrow for wood, so I needed something thinner, but still strong. After walking around in Lowes for a while I discovered that an light switch box with a blank plate would work very well. I also bought a 1/2" drill bit for the holes, and it turned out it was quite easy to put everything together.

I once made a servo controller for Brian Asman, and I already had converted that board for MIDI output. It turned out it had the right size for the box, and I therefore only had to add the PS/2 connector (I connected the data line to PORTB bit 4, and the clock line to PORTA bit 2. You also should connect +5V and ground. Wikipedia has a very clear diagram of the connector, but make sure you have the right mirror image (initially I connected it wrong, reversing the voltages. My keyboard was quite lenient, though). You'll know when you have the right connections if you see the keyboard's LED blink. To hook up the MIDI you need two 220 Ohm resistors for use in the data line and the +5V line. The data line should be hooked up to the TX pin of the PIC16F690 (you can also use a PIC16F688, if you want something smaller). The EMT-10E conveniently has a 9-12V output, which I use to power the box.

You can see and hear the box at work here:

The EMT-10E has a "split keyboard" mode and allows transposing up and down for several octaves, and it has a number of different instruments (no drums, unfortunately). The only problem remaining is that a PS/2 keyboard has auto-repeat on keys, which is undesirable if you want to play notes for a longer period of time (it also causes some notes to become "stuck", possibly because more press events are received than release events).

Here is the first version of the source code, which basically reads a key from the keyboard, converts it into a note value, and either plays it or stops playing it, depending on whether it is a key press or a key release.

If you're interested in this project you can always contact me and I can provide more details if needed.

Weighted Companion Cube

On a different note I decided to make a weighted companion cube a while back, as I was enjoying Portal a lot. As you can see it came out rather well, although the silver paint might be too shiny, and the sculpey turned out to look a bit like teeth.

Attempt at creating my own simple MIDI controller

I started on a new project, converting a cheap toy piano into a MIDI keyboard. The toy piano has 23 keys, which it reads using a 4x6 grid of scanlines. The resistors are already in place, and fortunately there are places for me to solder my wires to. The PIC16F690 should have enough pins (I only need 10, it has 20), and I already have MIDI code for my Beethoven playing box, that I described earlier. Hooking up a MIDI output is very easy as well: just connect +5V to pin 4 of a 5-pin female DIN plug with a 220 Ohm resistor, and hook up the TX pin of the PIC16F690 to pin 5. The step I forgot before is that pin 2 definitely needs to be grounded, so don't forget that. You can of course also use sketch one or sketch two, or any of the others found on the Internet.

I used the Pic kit 2 to try different voltages, and the MIDI works with my CASIO keyboard even at 2.5V. Since the piano has a 3V battery, I was glad to see this. Using 3V of course makes it not entirely MIDI compliant, but I'm sure most pianos will behave just fine with it.