

Ask HN: How to get simple gadget prototype built? - Jun8

There are tons of sites where you can list a software problem and people build to write code for you, similar ones for logo and graphic design, etc. Is there a similar site where you can specify the main idea of a simple electronic gadget and have a prototype built (cheaply)?<p>What I need is a stand-alone, self powered Bluetooth module that will continuously transmit a simple code (to be installed in large numbers in a store). I am a software person so don't have the slightest idea how to build a prototype.
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anrope
Doing accurate triangulation (localization) of a bluetooth receiver from a
bunch of active bluetooth nodes is maybe a little more difficult than it
seems.

Certainly a great idea in theory, but the accuracy of your localization will
depend on the signal propagation model you apply to the received signal
strength (RSS) that the phone provides. I would bet that it's difficult to
find a phone that will give you signal strength in dBm at a high update rate.

I worked on a localization project using passive RFID tags and an RFID reader
(a more power efficient setup than having active bluetooth nodes). Especially
in a store/mall type environment with many people moving around, I think it
becomes hard to get a decent model of expected signal propagation (mainly due
to constantly changing multi-path signal amplitude).

All of that said, for your application you might be able to get by with the
reduced accuracy (within 10 feet might work?).

With bluetooth, you also have to consider the number of connections a
bluetooth receiver can handle. That will probably greatly restrict your
density of nodes. RFID again holds an advantage here, in that RFID is a very
low-level interaction, while bluetooth is much higher level. This problem just
screams RFID. Too bad everybody's phone doesn't have a built-in RFID reader...
or a software radio!

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brk
I can help you with that. Email me if you like.

Hardware prototyping is a _little_ different than software proto's, because
you mostly incur real costs to develop things, which also makes mistakes
costly.

Depending on what you want, there is a high probability you can use COTS dev
kits and a little bit of a microprocessor (PIC, Atmel, Stamp, etc.) to make a
fully functional (albeit somewhat larger and more expensive than production
version) prototype.

~~~
Jun8
Thanks brk, I'll email you tonight to discuss.

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curt
If you want to have everything built you are going to have to use multiple
people: 1 for the enclosure and then another for the electronics and software.
Look on elance.com and guru.com use people ONLY with recommendations and
experience in what you want to do. Also in the req doc place a code or phrase
they need in the subject line so you know they read the req doc.

To buy parts: digikey, mouser, arrow

There are a ton of good prototyping firms in the US that will make you a
prototype within a week, once you have a design.

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stonemetal
There was a post not to long ago about a guy who made drum sticks that make
drum sounds as you beat them in the air. His first prototype was sensors
strapped to cardboard tubes. I would suggest doing something similar have your
first prototype be anything you can get to work regardless of form factor.
After you prove the concept then work on more realistic prototypes.

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retroafroman
This sounds like it could be better to use RFID. Depending on the application
of course. Could you go into more detail?

~~~
Jun8
The idea is the basic indoor mall/store navigation thing: Each BT transmitter
will send out a unique code tied to its location. An app on the phone detects
the nearest n of these and determines location by triangulation.

If the sensors are cheap, they can placed dense enough to provide pretty good
localization. The mall can pay for them. Say, if the transmitter is ~$5, we
can place 200 of these in a mall for $1K, which isn't that much, I think. The
transmitters should be low-power to minimize maintenance, e.g. go for a month
or more. They should also be small to be unnoticeable.

What do you think?

~~~
retroafroman
Hmm. I figured you were depending on people's phones to do the reading. I
assume you're doing this in order to help the customer navigate the store?

If you could have the customer pick up a handset RFID reader (with your app on
it I suppose?) that they return when they leave, RFID could work. I suggested
RFID because the tags don't need any battery or power supply. The readable
range might be a little less than with Bluetooth transmitters, but I have seen
read distances of 50 or so feet. And tags are cheap and readily available,
too.

~~~
Jun8
That is actually a good idea in settings where customers can/want to borrow a
device from the store or mall, e.g. the RFID reader can be incorporated into
the self checkout barcode readers that some supermarkets handout.

For a typical mall scenario, though, I think people will be reluctant to deal
with the hassle of another device.

~~~
retroafroman
Right, another device is always a hassle. Anyway, food for thought.

