Comments on: Capacitance sensor guide (AD7746)

By: robmora

robmora — Mon, 20 Jul 2009 17:57:36 +0000

@ dan:
Digi-key cheap? I suppose it’s all relative, as with everything else. (I still loves me my Digi-key however).

By: Bob

Bob — Mon, 20 Jul 2009 14:23:44 +0000

My gawd! $24.95 to sense touch? OUCH!!!

Whatever happened to the cheap $0.05 solution of using a resistor and capacitor pair tied to a port pin along with some simple code for sensing finger proximity? (OK… more like $1.50 at your neighborhood Sh!tShack store with their 3000% mark-up of repackaged surplus.)

Even a hard to find, overpriced, $3-$6 QT113G chip still needs a capacitor wired to it?

#2 (old school)engineering rule:
K.I.S.S – Keep It Simple Stupid

By: lekernel

lekernel — Mon, 20 Jul 2009 13:25:16 +0000

sure, and more interesting than arduino self-proclaimed “hacks”, but hey, it’s not what the masses like.

By: Agent420

Agent420 — Mon, 20 Jul 2009 12:28:09 +0000

I used touchpads from scrapped laptops for touch sensors before with an avr… works great, much cheaper.

http://forums.bit-tech.net/showthread.php?t=112110

By: tantris

tantris — Sun, 19 Jul 2009 21:05:40 +0000

Have a look at AD7147 and AD7150:

Cheaper ($3-$4), and AD7147 supports several input channels.Unfortunately they come in really tiny packages. Hard to make your own breakout board with these tiny leads.

Ironically, AD7746 is available as MSOP. You can solder it to a normal prototyping stripboard if you cut the stripes on the board in half.

By: googfan

googfan — Sun, 19 Jul 2009 17:38:21 +0000

You cant use this near rf sources, it goes crazy.

By: entropia

entropia — Sun, 19 Jul 2009 09:16:51 +0000

@lekernel

yeah, i’m getting tired of the arduinoaday.com too.

By: Dan

Dan — Sun, 19 Jul 2009 08:50:34 +0000

@lekernel

Yep. It’s called Digikey. A lot cheaper too, but perhaps too scary for most people.

By: lekernel

lekernel — Sun, 19 Jul 2009 08:34:05 +0000

is there a life beyond arduino, adafruit industries and sparkfun?

By: svofski

svofski — Sun, 19 Jul 2009 00:32:39 +0000

I made a capacitive sensor matrix 4×3 with little more than atmega8 and some caps. The performance you get with a micro is enough. These sensors are probably designed for something more sophisticated.

By: jproach

jproach — Sat, 18 Jul 2009 23:33:49 +0000

Yeah I’m not quite sure why anyone would use a $9 IC as just a touch sensor. There are many simpler and better options out there for button touch interfaces (or even scroll wheels, sliders, etc.). But I guess its a first step.

For a basic touch only option, check out the Qtouch chips and AVR Qtouch library.

Some cool things that the AD7746 could be used for: non-intrusive liquid level measurement, flow rate, various strain applications (pressure, weight), humidity sensing, etc.

By: therian

therian — Sat, 18 Jul 2009 23:03:37 +0000

I think I just too cheep when it
coming to parts, 90% of my parts coming from old VCR players and stereo

By: threepointone

threepointone — Sat, 18 Jul 2009 22:59:29 +0000

i’ve used the ad7746 before, and I can tell you that you can’t get the kind of performance you see in the 7746 with a simple transistor oscillator or a little microcontroller. you can measure ridiculously small capacitances with this guy if you implement it properly.

By: therian

therian — Sat, 18 Jul 2009 22:55:01 +0000

the cheaper way of doing is is transistor oscillator small capacitor and diode. or with little hacking single micro controller can handle this by it self