Ask HN: How to get simple gadget prototype built?
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)?
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.
14 comments
[ 2.9 ms ] story [ 16.6 ms ] threadHardware 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.
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?
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.
For a typical mall scenario, though, I think people will be reluctant to deal with the hassle of another device.
I think $5 is low. I'd guess more like $50 each for small quantity (<500) hand assembled in the US, using an off the shelf enclosure.
Does Apple even let you have access to the Bluetooth serial port profile?
So, you want to use a sensor type that a common smartphone can read, BT and Wifi seem to be the best choices.
Power wouldn't be a major issue, they would be plugged in to a wall outlet, or possibly even powered from a PoE line.
My mind is thinking about triangulation and the like. If the BT devices were networked, I believe you could have them transmitting an ID and a medium resolution time stamp. The phone would also have to be using network time and you could get a fairly accurate triangulation (again, I think, this part is far from my speciality).
There is a lot of merit to this idea. You could roll this into something to do with digital signage and advertising as well. As stores in a mall come and go, they have to update directories. You could build a system to let a mall auto-update it's layout maps as tenants change.
One thing about Bluetooth is that to get useful data sent back and forth you have to be paired and connected with the device. Essentially this means if you are talking to a bunch of different devices around a mall, all of the devices and also the mobile phone are going to have to be in constant Discovery mode to find/pair/connect with the new devices as you walk around. This is a more significant battery drain than just the 20/40mA of a regular connection for the devices and constant discovery on the phone is definitely super battery intensive. There may be ways around this, though, if you know the MAC address and/or are already paired with all of the devices you are attempting to connect to.
Pricing of just the BT modules themselves (CSR, etc.) is currently somewhere in the $7-10 range in quantity (10k), and that doesn't include the battery (Li ~ $3), and other PCB expenses.
Bluetooth Low Energy with auto-pairing, however, is going to make this process alot easier and cheaper, but we're probably 2+ years before its integrated into most smartphones.
Why not use GPS? The main problem to solve would be creating a database of the location of each store in the mall.
Did you find that there isn't enough GPS coverage in malls?
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!
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.