LFS: Radio Keyfob + receiver - Page 1
Forum section: electronics / general

author: mubes
author_rank: Regular Contributor
timestamp: September 17, 2014, 08:31:29 pm
content: Folks,Has anyone come across a source for 2 or 3 button keyfobsanda matching USB receiver? I'm in the UK. Finding keyfobs is easy enough, and there are plenty of relay/spi/ttl receivers out there, but I was hoping for a USB receiver that can plug straight into a PC and I was trying to avoid having to do any hardware development for what is a one-off system...my current best bet is a SiLabs-chip based receiver but I fear that will involve me in a chunk of coding that I wasalsotrying to avoid.These are for use as shot-clock counters for kids Ice Hockey....one at each end of the rink, reporting to a central PC.Thanks in advanceDAVE

author: macboy
author_rank: Super Contributor
timestamp: September 18, 2014, 03:54:28 pm
content: Use a RF receiver with TTL level outputs, and monitor those on the PC. If the PC has a parallel port, then maybe you can use that.Needs to be USB? Then try using a USB-UART converter (TTL level not RS232/DB-9) that has handshaking lines (DTR/DSR/RTS/CTS). You can then use the DCD, RI, DSR and CTS handshaking lines as digital inputs. You can open the (Virtual) COM port using whatever software you are using (even a scripting language) and monitor the status of the handshaking lines either through polling or events.If I was searching eBay for suitable USB-UART modules, I'd try using "USB (UART,serial,RS232,RS-232) ftdi". You will find plenty of modules looking exactly likethis one. Note the connections for the modem control (handshake) signals, that is the important part. Pick your favorite far east seller, wait 2 to 4 weeks, and start playing. If you want joy sooner, you can no doubt get identical modules from any domestic place hocking arduino-type goodies at several times the price, plus shipping.

author: mubes
author_rank: Regular Contributor
timestamp: September 19, 2014, 07:53:50 pm
content: Thanks for the note..Yup, that was pretty much my backup plan, but its a fair bit more work than find source, buy modules, plug in, use :-)I've have found some BT 3.0 'camera trigger' modules which look like a BT keyboard to the PC...they work pretty well but suffer from being short range BT. They have two buttons - one looks like 'VolumeUp' and the other one like 'Enter'...if the range were better they'd be perfect for what I need (the casing build quality could be better too, but that's secondary). They're CSR based but I have no idea if theres an easy cludge I can do to improve the range...I suppose I should investigate that, my previous experience of CSR is that it's not too easy to get info out of them tho.I have a BT 4.0 BLE module module on the way which might have better range, but I think I'm going to end up your route of hacking a 'conventional' remote plipper receiver :-(DAVE

author: SL4P
author_rank: Super Contributor
timestamp: September 19, 2014, 09:53:34 pm
content: Assuming you get the data into a USB port, what are you going to do with it?You'll need PC software to understand the USB stream - then display/whatever you want to do.If there's nothing off the shelf to do what you want, it's fairly trivial to use a low cost micro (PIC, Arduino etc) to handle the receivers, then generate a serial stream to feed the PC.The micro could also do the accumulation / tallying / scoring needed before sending the serial data to to the PC. Better still, let the micro drive the whole thing, remove the pC altogether.The 3-4 button Tx/Rx pairs often have a pin per button on the receivers, so pulling these into a micro is simple. What you do with it after that is up to you, but at some point you will need to get your hands dirty. It's a weekend project from beginning to end once yo have the parts.

author: mubes
author_rank: Regular Contributor
timestamp: September 20, 2014, 07:45:59 pm
content: Hi...the rest of the system is built...it's a JavaScript/JSON front end communicating to a Python back end on a linux server....the problem is I would like to simplify the devices the goal judges have to use (at the moment they get a web page) to avoid the possibility of things going wrong. You're quite right, it's just a weekend project, but I've got more than enough weekend projects in the queue already....RegardsDave

author: SL4P
author_rank: Super Contributor
timestamp: September 20, 2014, 09:44:42 pm
content: I envy your full life!I reckon hat you should spec it out, and approach a local teenager / hackerspace with a commission to put it together to your requirements.It won't cost much, and will come together without splitting your time too much.The components are out there, and when it all comes together, will be simpler & more reliable with the attention it gets.Yuo get to be a project manager/customer and perhaps end up with a saleable project!Keep us informed how it goes.