Schematic for tanjent’s “bliplace”

Yesterday, I wrote about soldering together my bliplace kit. Today, I thought I’d have a peek at the code and the schematic. Here’s the schematic:

Not much there, but a couple of interesting things. The microphone is an electret, which needs some power to be functional (supplied through the 10K RU resistor). To me, the capacitor CC and the RD resistor look like a high pass filter, with the supplied values the cutoff frequency is nominally about 160Hz. Not 100% sure I understand how the capacitor CN or what the overall input impedance is for the ADC input pins on the Atmel chip, so I am not 100% sure I understand the subtlety.

I also thought that current limiting resistors were interesting. The center LED always seems to glow brighter, and this seems to be because R2 is only 100 ohms, compared to the 1000 ohms that were used for the other two. I also wondered about the LEDs: this gadget is powered by a single 3V cell. The ATTiny25/V can run down to 1.8 volts, but I thought that white LEDs had fairly high forward voltage requirements. For instance, this page on Wikipedia says that the typical voltage drop for white LEDs is around 3.5 volts. I don’t have a lot of white LEDs lying around, but it does suggest some experimentation.

Antenna? Who needs an antenna?

Drew, KO4MA, didn’t let a little thing like the missing antenna on ARISSAT-1 keep him down. He aimed his antennas at the satellite, and recorded the following:

What’s goin on here? Drew has a pretty good antenna setup, which includes an M2 CP42 for the uplink. That provides about 16.8db of gain. Since the ARISSAT-1 receiver was supposed to be reasonably sensitive to be workable with portable equipment, that gain is enough to put a reasonable signal into the transponder. I don’t think I am going to be working the bird with my setup, but i suspect that there are quite a few amateurs with similar setups that could still work ARISSAT-1 even with its lack of antenna.

Very cool.

Addendum: I was rereading my posts from yesterday, when the frustration of deploying ARISSAT-1 with a missing antenna was fresh in my mind. And I do frankly admit to a fair amount of frustration with AMSAT. But I was reading some even more negative traffic on the amsat-bb list, and that put it in a bit of perspective for me. ARISSAT-1 wasn’t a waste, nor is it useless, nor was it a bad thing for AMSAT to invest in. In terms of its primary, largely educational mission, I suspect it will be quite successful. Several times during the NASA briefing yesterday, they mentioned that this was the first of a series of educational birds to be launched from the ISS. These launch opportunities are incredibly valuable to the amateur community, and we should make sure that our frustration with problems doesn’t boil over into lashing out at our allies who are helping us achieve our goals in amateur radio and space.

Building tanjent’s “bliplace” kit…

I was in the mood to melt some solder, but didn’t really have a lot of time and/or brainpower last night, so I turned to my box of little electronics kits that seems to have been growing over the last few years. I located a small plastic bag which contained tanjent’s “bliplace”, a tiny kit that he generously was handing out at a conference we both attended. It’s simple: an Atmel ATTINY 8 pin controller, three caps, five resistors, an electret microphone and a battery is all it takes to get it to run. I figured it would take me about 20 minutes to assemble. It took about 35, mostly because I wasn’t paying attention and soldered the first two resistors in the wrong place (the board has a very symmetric layout, and I got turned around). That got me some practice in using my solder sucker, and had to solder in two new 1K resistors from my junkbox. But in the end, it worked!

What is bliplace? In his words:

Bliplace is a wearable, hackable, sound-activated blinky light toy. It uses a small microcontroller and a mix of hardware and software feedback to automatically synchronize with and adapt to the sounds around it – it should pulse along with the ambient noises around you no matter if you’re in a quiet park or a thunderously loud concert.

Here’s the video of the thing working. Pardon the sound levels when I turn the radio up, I shot and edited this on my iPhone.

It’s a clever little gadget by itself. But what’s especially cool is that it is open source. You can get the board and schematic files, Gerber files, and the source code for the firmware. I think it would be interesting to make an “amped up” version of this thing, which would drive some big power transistors to switch some truly high power CREE LEDs. The code is released under the MIT license, so modifications should be easy and redistributable. It should be trivial to get this to run on the Arduino platform as well, which will make experiments easier for the wider audience.

I’ll be staring at the code a bit harder over the next few days. Stay tuned.

ARISSAT-1 Update…

Okay folks, I’m sorry, I promised that I’d try to stay up late enough to record some of the first passes of ARISSAT-1, but physical need for sleep outpaced my natural enthusiasm and curiosity, and the first good pass found me sound asleep. Through some perverse quirk of fate, all the best passes of the ISS are occurring in the early morning hours. Running my own homebrew satellite prediction library, I find that my best opportunity for a pass where I am awake and the satellite is illuninated, and therefore in high power mode, will likely be tomorrow starting around 7:28AM PST. I’ll try to get myself all setup for that, and will hopefully have some audio and/or video tomorrow.

In the meantime, it has been heard.

VK2BRB recorded this YouTube video:

SW1OBT heard the voice beacon, and the start of the SSTV transmission: