DIY metal stencils – video update

UPDATE: See the “definitive tutorial” post on how to make these.

I posted this video of the latest SMD stencil I made for my Moteino project. I ended up shrinking the pads by 8mil on this one, the reason being that the previous stencils I made I shrunk by 5mil and the stencil would dump too much solder paste, causing some solder bridging. See the stencil step through post for details how to make this.

I also discovered another very good method to transfer toner: silicone coated paper. I wiped a very thin layer of clear silicone on a blank sheet of paper (on half of it). After it dried I printed the mask directly to it. The iron method will give very good results, the toner will either transfer 100% or not at all. The spots where it doesn’t transfer are fixable with a thin Sharpie pen. The tool you use to spread the silicone has to be very flat and even, any unevenness will result in less perfect toner transfer.

Moteino programming jig

Once I assemble Moteinos, I will need a way to load the bootloader and test programming from the Arduino IDE. Since I plan to sell them without soldered headers (unless people want that option), it’s impossible to easily program the ATMega328P chips after the boards are assembled. Unless … I use a programming jig, a perfect DIY project to help in the Moteino manufacturing process.

Steps for making the jig and programming a Moteino:

  1. I ordered some spring loaded test probes (aka pogo pins) on ebay
  2. I used 2 Moteino PCBs to align and hold the pogo pins in place
  3. The bottom PCB is soldered to the pogo pins, the PCB in the middle is used to keep the pins straight and aligned. This can also be soldered.
  4. I only soldered enough pogo pins to be able to program and test the on-board LED and the transceiver. If those connections work, the other Moteino pins are almost 100% guaranteed to work.
  5. Connect the AVR programmer and the FTDI adapter/cable. The FTDI adapter provides power, the AVR programmer expects the board to be powered separately.
  6. Set the fuses and burn the bootloader with the AVR programmer
  7. Load a test sketch (blinky)
  8. Finished

Simple ATX bench power supply

ATX_bench_supply_parts

For some time I had this old ATX power supply gathering dust and getting moved from one place to another. I kept wanting to transform it into a bench supply. ATX supplies are switched power supplies that can provide a lot of current. They have a set fixed of voltages (5V, 3.3V, 12V, -12V), nonetheless very useful for most electronics and low voltage high-power projects. Once nice thing is that you can combine outputs to get less conventional voltages, for instance you can use 3.3V as GND and 5V as VDD to get an effective 1.7V potential difference which could come in handy in some projects; you could also use -12v as GND and 12V as VDD to get a 24V range for your project. Be warned if  you try that though – if your project has other GND sources that are connected to mains ground/earth you could potentially cause some sparks/smoke/flame/fireworks, since all the grounds in this supply are directly connected to mains earth – as revealed by a simple connectivity test between the supply input and output ground terminals.

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