I have been quite frustrated using generic Arduino Uno boards with peripherals such as digital compass, IMU, and nrf24L01 radios. The problem usually manifests itself as not enough usable I/O pins, not enough power or ground pins, wrong sex on headers, an most importantly,insufficient 3.3V power. I have boards from Dagu & RFRobot that satisfy most of these issues but I need the Uno pin format to cleanly interface with the Dagu Scamper ComMotion shield.
Solution. Design my own board.
- Compatible Uno headers
- Additional 3 pin headers for all I/O.
- Beefier 3.3V and 5.0V regulators
- Dedicated 8 pin header for nrf24l01 radio.
The schematic is ready and the art work is 90% finished. The board outline is currently a little longer than the Uno due to the current position of the nrf header Nothing is cast in stone and I will abandon this activity should a viable commercial product present itself. I will appreciate feedback on features and possible power options.
I am most uneasy about merging power from the USB port and external battery. Currently have a jumper to select one or the other.
The board has been designed using the GNU schematic capture and PCB layout tools. Plan is to use OSH Park to fab the first 3 boards and then one of the China shops for the next batch. It usually takes me 3 revisions to get it right.
I finally have the schematic and artwork ready. Provisioned for three 500ma 5.0V and one 500ma 3.3V supplies. Boad is slightly larger thn the Uno but retains the mounting holes and female header alignments. Attached are pdf & png images of schematic and board. Please review and comment.
I will post the original gEDA design files in a couple of days when I place order for boards. I am currently ordering components to verify that the selected packages are available. Also will tweek the pad sizes to make hand soldering easier.
Accepting names for project.
Added suggestions by LMR members that included dedicated I2C headers, Vin pins for servos. Also reverered power and ground on 3-pin headers to align with servo connectors. Found and fixed a of missing trace and revised some footprints to reflect purchase options.
My current major concern is the power. The regulators are really small. Their specs say 500ma but that needs to be verified.
I want to add a 3.3V/5.0V option for the I2C power. Space is tight so it may be a solder bridge rather than a jumper.
Changed project name to "mab" my-arduino-board. Attached files reflect today's edits. I plan on submitting artwork for PCB's on Sunday.
Updated schematics and artwork to support servo headers on ports D5, D6, & D7. Also routed Vin thru 2 diodes (OddBot suggestion) for powering servos. This works nice with the Dagu Scamper which has 6 AAA batteries. Also will work with 7.4V LiPo's. Made board slightly longer and got rid of traditional Uno outline.
Tommorow is order day.
Order day came and went. Mostly obsessive compulsive nit-picking cleanup on my end . Added some filer caps and tried for more spacing near my solder joints. Big change was the small 603 caps are now on back side.
OSH Park PCB service renders images of the board prior to committing to build. Great feature. This time the drill image was blank. There is a problem (probably mine) that need to be resolved. The blank boards will cost just under $10.00US each. Added gerbers for viewing. Do Not use for ordering!!!
The boards have been ordered. Gerber drill file problem was just with the OSH Park image rendering software, not with the design files. Appears fixed. Time to make a BOM and get the electronic components.
Boards arrived from OSH Park. As usual they look great. At least until I take a solder iron to them. Forgot to make the BOM and order parts.