This variation on my Digital Setting Circles project was created by Craig Combes. He provided the following content so others could recreate his version. Thanks, Craig!
Many people use Dave’s serial DSC board with a serial to Bluetooth adapter and that can get quite pricey, large and power hungry. So I adapted Dave’s design to skip the RS232 circuit and go straight to Bluetooth. In the process, I decided to change the PIC to a less expensive, and more recent chip: the 16F628A, which Dave had code for already. I made some minor tweaks to the code to eliminate some pull up resistors.
The new design uses a 5 volt regulator (to make sure the encoders are happy) and a 3.3 volt regulator to supply everything else (the Bluetooth module needs 3.3v). I used a MOSFET for polarity protection to reduce the input voltage requirement. I also replaced the oscillator module with a crystal to reduce cost and power consumption. The Bluetooth module is a surface mount device and the boards I created have 11 pads to solder for this device. Most of the other components (not the PIC) are surface mount also, but there aren’t many of them and their are only a few pins maximum per component to solder, so it’s not difficult.
The Bluetooth module is the RN-42 from Roving Networks, which only uses 30ma when transmitting, 3ma when “sniffing” and 26ua when sleeping. I have it configured to communicate at 9600 baud. For more info on the RN-42, you can go here:
D1 is the power on indicator LED. SW1 is the reset button for the RN-42 and the PIC. D2 is the status indicator light for the RN-42. D2 blinks until connected, then it stays on.
I do have boards made for this circuit and I will eventually make them available through FAR Circuits, like Dave’s original board. I am open to suggestions for improving the design/board. Just send me a note here.
Here is the schematic diagram (click to enlarge):
The parts list:
|Part||Description||Mouser Part No.||Price|
|R1 & R3||470 ohm resistor|
|R2 & R4||10k ohm resistor|
|R5||1.6k ohm resistor|
|C1||10uF 15V aluminum electrolytic capacitor|
|C2, C3, C6||0.1uF 10V (or greater) capacitor|
|C4, C5||33pF 10V (or greater) capacitor|
|U1||UA78L05 5v Voltage Regulator||595-UA78L05ACPK||$0.48|
|U2||UA78M33 3.3v Voltage Regulator||595-UA78M33CDCYR||$0.60|
|U3||Microchip PIC16F628A Microcontroller||579-PIC16F628A-I/P||$2.07|
|U4||Roving Networks RN-42 Bluetooth Module||765-RN-42||$19.95|
|SW1||Normally Open Pushbutton switch|
|J1||Dual RJ-11 jack|
|X1||Crystal ±20ppm 4MHZ Fundamental||815-ABL-4-B2||$0.39|
Here’s a picture of the completed board (click to enlarge):