I'm wondering about the feasibility of adding a Bluetooth module to my electronic weighing scales so that the result can be sent to a computer. I know nothing of electronic d-i-y.
(1) Is this feasible?
(2) Is there a more appropriate newsgroup to ask this question on?
Yes, but not with your skill level. You're probably looking at at the very least several months of study first, there isn't a simple way of doing this. The simplest way is probably to find some industrial scales with a serial output, then send that wirelessly with existing hardware.
Bluetooth still isn't there yet.
Yes.
You need a scale with a serial / RS232 output. Building your own, or adding one to a non-output scale would be hard.
A PC with a serial input, already running software that expects to receive input from a weighing scale.
A pair of 418MHz radio modules (or whatever the Euro-ratified frequency is this week) with serial IO. These can be used to make a "wireless serial lead" - you just stick the scale up one end and read the other with a PC - it's completely transparent to the devices connected.
Maybe Excel or something as the final data capture. Some scales come with software that can act as a driver for this, and the rest is a simple-ish Excel macro.
Yes - a whole bunch of electronic groups.
Do you mean that there exist weighing scales with a serial port, or other way of connecting to a PC? If so, where can they be found?
such as ... ?
Ebay?
Now, click "search titles and descriptions".
At the moment, there are a few available internationally, but they should give you an idea of where to look, even if you don't want to buy.
Just Google "RS-232 scales price"
Here's one of many
Thanks for the suggestions. I looked around at eBay and with google, but all the weighing scales with serial or USB ports that I saw seemed designed for lab work, and were absurdly expensive.
Surely it can't be that expensive to add a WiFi or bluetooth module to broadcast the signal sent to the LEDs in an electronic scales?
If it were a common requirement, then mass production would make such an addition relatively inexpensive. But it's obviously not. Perhaps most drug dealers that seem to have forced down the price of small accurate scales don't yet use a laptop to record their transactions?
Yes, it is expensive and difficult. In a nutshell, the info sent to the LED is not in a language which a PC will understand - only the LED screen - hence you need a scales with RS232 output - or build one from scratch with a strain guage - but this is far more complicated that you want to do!
If you can find an LED scale, then it is indeed reasonably easy. The trouble is that LEDs are rarely used these days, and LCD or vac fluorescents are harder to "read". LCDs especially, because the coupling between one tiny chip and one tiny display can be an enormous task to tap into.
For a one-off, then I'd look for a scale with RS232. Unless the time and trouble of someone who's competent at working with TINI boards, PICs or similar is zero-rated, then they're going to cost more.
Lab surplus dealers would be my first port of call for finding a cheaper scale with RS232 already.
You may even find a scale that offers an RS232 option in the range, just not installed on your "cheap" model, but can have it added internally with just a few components. This is rare and lucky, but I have seen it done.
Look again. There was someone on ebay selling scales to 150Kg, for $30. Shipping would be a bit expensive. $100?
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