Monday, June 13, 2016

100: Avoiding Solder
-- revised, again --

This is a recurring theme with me. I hate soldering, especially teenie-tiny, close together connections. So I keep looking for alternatives -- like screw-down connectors, circuit paint -- and just now "Wire Glue." See my posts 59, 93 and 96.

What's wrong with Wire Glue? a) it was hard to mix up (settled in the bottom), b) very weak "glue"; but here's the real problem:

Here's the test: I measure a known resistor. In my test below, a reading on a 220 Ohm resistor.
Big surprise, it reads .220k Ohms

And here's a reading for a heavy 3/4" line of Wire Glue (on inkjet printer paper):
Wow! 611 Ohms

This stuff should be called "liquid resistor." You will add resistance even if you glue 2 wires together with no apparent gap. PS: a foot long jumper wire reads .0.

Meanwhile, on the insulation front I have tried a couple glue/caulk products. 

Above, the glued wire-ends are both about 1mm apart and after 24 hours curing there is no current leaking between them. I made this test because I felt that red tube was the better insulator (they are the same). The main problem involves the tubes both drying out so that the screw top is plugged within a week or so. Also, the green tube goop sets harder.

More about glue:
My experience with "super glue": not an insulator. And about epoxy: probably not surprising is only a little stronger resistor than the above Wire Glue (and much stronger glue).

black tube 'contains metal'

Friday, June 10, 2016

99: Dog Toy

I have a mad urge to build an interactive amusement for the left-at-home dogs in my extended family. Yeah, I know other people have-done/are-doing this. So what.

I figure on implementing the following features using both a Raspberry Pi and an Arduino Nano.

Things I could provide:
1. Call to the dog -- recorded voice.
2. Show pictures or video clips of owner.
3. Play animal video clips: e.g., squirrels, lambs gamboling.
4. Dispense treats when dog touches proper button. (indicated by voice and LED)
5. React to the dog via motion detector.
6. Take video camera stills.
7. Via smartphone web page:
   - Turn the system on or off.
   - activate different "programs".
   - Keep track of treats supply.
   - Play back today's history of access.
   - Upload images (low-res, B/W) image from the camera.
Equipment (wifi & Internet assumed):
Raspberry Pi system -- $100
Arduino Nano (control motor) -- $10
Video monitor/speaker -- $50
Stepper motor -- $10
2 Photosensors -- $2
PIR motion sensor -- $2
2 Capacitive touch sensors -- $15
LEDs -- $1
Pi Camera -- $30
Box -- $30
Temperature sensor -- $1
Wires, other Misc. -- $20