Some changes from REV 3 to REV 4.
Render of the PCB from OSHPark.
Top stencil pattern. The through hole pads on the micro USB connector are going to be soldered with the “Paste In Hole” method. I have not tried this yet but if it works I will be able to cut out an entire operation during production of the boards.
Finished the next revision of the Propeller Development Stick REDUX. The power switching has been changed to fix the flakiness of the past revision. I switched the TPS2115 to a TPS2113. This seems to have fixed the weird power switching issues. The layout has change completely. SD card slot is on the top side of the board and the power circuity and ADC are on the bottom now.
I had a couple spare PSOCs to test the part tray with and train the pick and place. The PSOCs fit very well with little wiggle. Will be training the machine on the placement of the parts on Friday.
Here is a short little video of the pick and place positioning the FCC connectors onto the PCB panel. I am using double sided stick tape to replicate the holding force of solder paste. The pick and place is running at 10% speed to prevent the connector from sliding off the nozzle.
This is the screen printer we are currently using at MacroFab. It is an old semi-automatic printer but it works well for its age. It has a vacuum table to hold down the pcb and suck the screen to the pcb. Put some coated stainless blades on it for smooth paste squeegee action.
The Pic-32 on the Pinheck Pinball System is a TQ-100 package which is .4mm pitch. We used a solder stencil and placed the part via the pick and place. Stencil was .1mm in thickness. Ran 25 boards and had no solder bridges.
At MacroFab, I have been working with a DP2006-2 Madell pick and place for the past 6 months doing low scale pcb manufacturing while we test our software on it. Some parts (like big MCUs and connectors) come on what is called a tray where the parts are laid out in a X-Y matrix. The pick and place machine knows the amount of parts and the offsets so it can pick up the parts in the tray.
For one of the jobs we are doing I needed two trays, one for the PSOC4 and another for the FFC connector for the LCD. The DP2006-2 is pretty limited in pick and place area so I decided to make a part tray that would hold both parts. First I measured out the metal tray area on the DP2006-2 and looked at the datasheets of the parts for the physical dimensions. Then used SketchUp to draw out the tray. I gave each part .15mm clearance around the maximium size of the part. This takes care of any tolerance issues. If the tolerance is to big then the part can become crooked in the tray and the machine might have difficulties in picking up the part.
The Sketchup file can be downloaded here and the STL output for a 3D printer can be found here. I sent the files over to my friend Chris Kraft who printed the model with his MakerGear M2.
Chris sent me the model along with some test squares so I can test the ESD spray paint adherent to the PLA material the part tray was made out of. It adhered just fine to the bare PLA material so I went ahead and sprayed the part tray.
So far I have tested it with the FFC Connector and it has worked great! The PSOC4 fit but I have not trained the machine on it yet. I will post a picture when I load them into the machine.
Finished drawing the case last night for 3D printing. Used SketchUp to draw it as its free. Still searching for that perfect 3D modeling program. SketchUp is an ok piece of software. Compared to AutoDesk 123D V9 it lacks some features but the newer 123D Design (they changed the name slightly) its pretty lame.
X-RAY view for giggles.
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.
Above is the REV 1 of the OctoPROBER. This revision fixed allot of the issues I had with programming the propeller and the propeller resetting when the USB plug was plugged in. To fix the USB resetting the propeller when being plugged in I disconnected the reset line off the FT230X (USB chip) from the reset signal on the propeller. This breaks being able to program the propeller as it needs to upload code directly after start up. To fix this problem the code has a menu option that will reset the propeller if it sees the USB reset line so the user can control if the USB resets the propeller or not.
To enable ease of first time programing or encase the firmware gets borked there is a switch that manually connects the FT230X reset signal to the propeller reset signal.
Rev 2 of the OctoPROBER I decided to do away with the MAX31855 chips. They are very expensive ($5 a piece) and not very accurate (+-2C). Instead I am using 2 MCP3424 18-bit ADCs to do the thermocouple readings. To perform cold junction readings I am using 8 AT30TSE752 board temperature sensors. This should provide +-0.5C accuracy and the ability to use any thermocouple type.
REV 1 boards arrived today. Will be assembling one when the parts arrive. I might have to make another revision after this to add a filter to reduce the jitter on the MAX31855 thermocouple chips. Right now the ripple on the 3.3V line is around 40mV which causes the reading to fluctuate a bit. A low pass pi filter will fix this issue.