- PIC16F88 running on internal 8MHz Clock – low cost and very popular, free development tools available, i.e. C compiler.
- Works in unlicensed 915MHz ISM Band(Australia/US), can work at 433Mhz by changing RF module(US/EU/Australia).
- RF uses FSK Modulation – Less prone to interference sources.
- All aspects of the RF module is configurable via the firmware, i.e. frequency, Tx power, receiver bandwidth, modulation, datarate etc.
- Indoor Range – ~30m+ works all through my house non line of sight, i.e. through multiple single brick walls, with transmitter at furtherest end, close to AV, TV & WIFI (i.e. interference sources) and receiver roaming throughout the house in different rooms, microwave oven also in the mix. No packets lost or dropped so far, but more testing needing to be done.
- Outdoor Range – Untested, but from indoor tests I would guess 150-250m easily.
Update: Outdoor Test Results here
- Antenna – Simple 8cm whip (i.e. a single piece of wire), these RF units are matched to 50Ohm so an SMA antenna could be used
- Sync to 1/125 – in theory it could easily sync upto 1/1000 as the Rf modules are capable of the bitrate necessary, however range will be affected by the higher the speed, also the processor / oscillator arrangement may need to be revised to handle the higher interrupt rate to process data, i.e may need to use a chip with onboard SPI support etc.
- Can act as Master or Slave.
- Can be programmed to use any frequency from 902Mhz to 928Mhz (using the 915Mhz module), using the 433Mhz Module will allow similar channels.
- Can be triggered by a contact closure on Trigger Input. i.e. from camera
- Can be manually triggered by test button.
- Trigger output is isolated upto 400V, i.e. can safely trigger old stobe units with high voltage on hotshoe / sync terminals
- Powered by x3 AA batteries. Currently no power management in the firmware.
- Cost per prototype board AUD$ ~25
Note on the costs:
- Most components are sourced via local retail outlets so are probably definately more expensive that sourcing elsewhere, i.e. this can be built a lot cheaper i.e. Sub $10 in parts.
- Some of the components I had lying around at home so I’ve just used market prices in my estimates.
- No freight was added to construction costs.
- Some components have minimium order quanties such as the RF module.
During the development of the StrobIt Open Trigger Project I’ve been using the HopeRF RFM12B Tranceiver as the RF module. The learning curve was fairly steep so I’ve decided to create a series of How-To articles so that others can easily get the module up and running fairly quickly for their project of choice. So far I’ve already slated these for use in a few other projects around the house, both robotics, home control and weather station related.
After a hectic and very hot Christmas (41DegC) I managed to get some development time and finished 2 prototype boards. My RFM12 header boards still have not arrived, caught up in the christmas mail I guess 🙁 So I’ve had to resort to hand soldering some wires to the header in the meantime. (Murphys law suggests that as soon as I finish soldering these headers the breakout boards will arrive in the mail)
Tomorrow/Later tonight I will test both of them and see if I can get a remote trigger happening woohoo.
Sorry about the quality of the photos as they were taken with my phone 🙁
A couple of design changes, main one being I could not physically fit a single design into the existing housings that would encompass the Tx and RX, the RX housing is the problem as it’s a fairly small board so that means I’ve had to change the processor so that I can physically fit everything as well as the RF onto the board, so now a single design using the PIC 16F873A now becomes 2 circuits, Tx and Rx using a PIC16F88 as the MPU.