Testing the standby current draw for the OctoPROBER. It uses a soft power switch and a real time clock which draws power when the device is turned “off”. Fortunately the power consumed is very small. At a battery voltage around 4V the standby current is under 20uA. With a 2000mAh battery we have a standby lifetime of 100000 hours or over 11 years! Don’t really have to worry about the OctoPROBER loosing its clock time anytime soon.
Three boards arrived from OSH Park today. First 4-Layer board I have ordered from them. Quality is pretty good. Silkscreen is a bit weak but that is probably due to me running the weight of the text to thin.
Internal two layers are GND and 3.3V. Outside two layers are signals.
Close up of the kickass OctoPROBER logo.
Character display mounts on the back of the PCB. This way the PCB can be mounted to the front of the case without silly long button caps on the tact switches.
Finished REV 0 of OctoPROBER last night. I added a MCP3021 which is a I2C 10bit ADC with one analog channel. It will be used to monitor the battery voltage and indicate when the lithium battery is close to being dead.
Schematic is a bit of a mess but I will be cleaning it up.
Files are on GitHub. Will start programming the hardware test software this weekend for the propeller.
This has been an idea I have been kicking around for awhile. The OctoPROBER is a 8 channel, K-type thermocouple temperature logger. It has a micro SD card slot for logging data remotely. The USB connection can send log data directly to the PC.
Power is supplied via internal lithium 18650 3.7V cell and is charged over USB. The BQ24075RGTT is used to manage the charging of the lithium battery by using the outputs of the FT230X USB chip. I will cover this in more detail when I can verify my idea will work.
To prevent corruption of the SD card a soft power circuit is employed. A single optocoupled output is given to allow control of an external circuit.
The VCNL3020 Breakout Board Rev 0 is complete. Added some vias to stitch the ground planes. I already have some ideas to make this breakout better. Going to add a solderable jumper and a space for a 3.3V regulator so it can be used with 5V I/O systems.
I just finished updating the design page.
Last night I soldered the new REV 1 board. Everything is working correctly and the footprints/silkscreen are also correct. Will be working on the page documenting the progress of the PDS. Will also upload the design files.
Progression from the first PDS on the left to the newest one on the right. Slightly longer but slightly thinner now. Changed the USB port to a micro usb port. Added an ADC and mirco SD card slot.
Layout of the PCB.
Just finished cleaning and soldering the first board for Tommy. I managed to get the connectors that did not fit on by sanding a bit of the plastic off. The footprints where off by 0.5mm.
The only thing I am waiting for now is my PC power supply (I knew I shouldn’t have tossed those when I moved…) to test the hardware. When that is done the board is heading over to one of my friends so he can program the ASM drivers that will run the system.
After that I will order Revision 1 which has currently all the corrections to the footprints and spacing issues. Once that version is verified I will release all the design docs to open source the project. I could do so now but I would hate if someone ordered the board and it didn’t work.
Finished REV 0B for the Prop Dev Stick. I minimized the size of the board from 1.5″ to 1″ wide. It is now thin enough to plug into a bread board. Width between the two rows of headers is 0.9″.
Some quick specs. Running the propeller at 96MHz, Micro SD card slot, 4 channel 8-bit ADC, built in USB, and all I/O brought out to the edge. A power MUX controls whether or not the Prop Dev Stick uses USB power or power from an external source like a battery. This way you can have the unit running off battery or solar and still use the USB connection for serial data. When an external power source is absent the mux switches over to USB power.