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3" distance wireless link
NFC (as has been mentioned) might work.   Interesting app note on using smd inductors as antennas.  http://www.st.com/web/en/resource/technical/document/application_note...
Monday, 27 October 2014 - 11:44
USB<->RS232 - slightly off-topic
I've noticed Bray's dropping chars in the past. Especially with large amounts of fast 'bursty' data. It seemed related to the windows screen update. I noticed if I minimized...
Thursday, 10 July 2014 - 09:32
Pen to mark IC chips
Edding sells refill ink for some of their pens. Buy in bulk. Related, lots of different specialzed marking pens available. http://www.markingpendepot.com/ -carl
Wednesday, 22 January 2014 - 19:54
Reading 1Mhz SDLC data
I did an SLDC project a few years ago. I was just able to reliably bit bang decode 115200 data on an atmega running at 16mhz. Encode was much easier. I think a 1mhz data rate...
Wednesday, 8 January 2014 - 22:22
Magnetic Sensor - Looking for ideas
SPDT reed switches feeding a flip-flop debounce circuit? Then just straight into an AVR counter. Seems simplest. -carl
Sunday, 22 December 2013 - 21:34
Magnetic Sensor - Looking for ideas
Hard to beat reed switches for low power. I'd probably debounce and run into an external cmos counter. Wake up at timed intervals and read the counter. It's the way those cheap...
Saturday, 21 December 2013 - 15:42
Pen to mark IC chips
Paint markers also work pretty well on these surfaces. http://www.sharpie.com/enus/pages/oil-based-paint-marker.aspx Can find at stationary and art/craft stores. Not sure how...
Saturday, 14 December 2013 - 13:49
attiny wearable badge - battery question
The TP4056 looks like pretty good & cheap chip. Think it's used in all the e'cheapo chargers I have around here.(That flickering charge led when no battery is connected is a...
Saturday, 14 December 2013 - 13:32
NRF24L01+ Send Only? (Solved)
Was the socket confirmed to be the real cause of the problem? If you just swapped modules around and it started working, be very careful of some compatibility issues on those...
Friday, 13 December 2013 - 16:20
attiny wearable badge - battery question
lir-2032 (or lir-2450 for more current) https://www.fasttech.com/products/0/10003758/1270801-lir2032-36v-rechargeable-lithium-battery-w-prongs- MCP73831 with the charge rate...
Friday, 13 December 2013 - 15:57
Quick SPI question with Multiple Slaves
Life is easier with schematics. http://www.elecfreaks.com/wiki/index.php?title=SD-MMC_Cards_Breakout_Module -carl
Wednesday, 20 November 2013 - 23:26
Quick SPI question with Multiple Slaves
At first I thought that SD card breakout had resistor divider level shifting going on. Now I'm not too sure. Looks like the resistors are just pull ups to 3.3V. You'll need to...
Tuesday, 19 November 2013 - 21:47

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