Received TinyTimer-Duo boards and then ordered a new set

I received the boards for the TinyTimer Duo… and confirmed that they too had two mistakes.  I corrected the mistakes and ordered a new set.  The following changes were logged:

  • Fixed Oscillator and capacitor sequence.
  • Added 10K resistor to reset button
  • Changed labels on logic inputs to reflect the pin they connect to
  • Changed filter capacitors on switched circuits to use the new capacitor I found from Mouser that is rated for higher voltages and has a smaller footprint.
  • Changed label on ISP
  • Added ground plane to bottom of board.
TinyTimer - Duo

TinyTimer – Duo

New Kit – Mini-button

I decided to make a small board that can be used to mount tactile switches to breadboards.  There are other products out there that do this, but most of them are not kits.  This should be a very fast “product” from design to launch.  A dozen boards are on the way.  Each board measures .34x.5 inches.  It’s designed to use a through-hole Tactile switch and standard 2 pin header.  I anticipate offering these in sets.  For example a set of 5 PCB’s or a set of 5 PCB’s with parts for assembly.  I’m anticipating that the PCB’s will be around 50 cents each.

mini-button

mini-button

New PCB design for TinyTimer

  • replaced switch with pin-header and shunt (jumper).  This is more cost effective and avoids the switch footprint issues.
  • rearranged the crystal and capacitors to ensure no routing errors as on the previous PCB.
  • added a ground plane.
  • located all controlled circuit traces to top of PCB.
  • changed axial capacitor out for more cost effective equivalent capacitor with higher voltage rating (600v old component, 1000v new component).
  • Adjusted component layout to produce traces with fewer vias.
  • Adjusted holes in PCB for mounting purposes.
TinyTimer-KS PCB Design

TinyTimer-KS PCB Design

Bug Juice – found the error in the schematic

Prototyping is one of those things that when it works properly it can be irritating.  I found the bug in the circuit this evening.  I had the crystal oscillator and the capacitors in the wrong order.  Grr.  I’m going to salvage the prototype board, but it won’t be pretty.    Of course, the important part is that I found the mistake and didn’t make 100 copies of it.
That’s the joy and purpose of prototyping.  Here is my 6 component Hackduino running BLINK.  🙂

Barebones Arduino Test

Barebones Arduino Test

Tinytimer-KS Prototype Board first look

I’m excited to share that the prototype board has been assembled.  I did discover an issue with the run/program switch.  A few other minor adjustments were warranted as well.  Still working on getting the ISP to behave.  The assembled board looks good.  Here’s a picture:

TinyTimer-KS-Prototype-Assembled

TinyTimer-KS-Prototype-Assembled

I worked on this for several hours yesterday.  Realized I’m short some of the tactile switches and low on a few other components.  Ordered more pieces.  ISP would not work.  Kept getting 0x00 response from IDE.  Going to take another board and populate it with just the bare minimum pieces and see if it will work and then add to it from there.  There is a bug somewhere.  Only thing new is I’m using a different Arduino footprint from Sparkfun’s library.

 

Testing a transistor, relay, resistor combination to ensure long term success

I originally designed the tiny timer using an MJE3055 transistor.  I did this because I had one laying around.  Always a great excuse when hacking a project.  For production purposes, that’s not usually the best choice.  I decided that I would change over to one of my favorite transistors, the BC517.  It’s a high amplification transistor with an Hfe rating of 30,000.  This means that the signal amplification is 1:30,000.  The first time I put a timer together with it I promptly fried it.  That was unfortunate but a stark reminder to always check resistor values.  So today I setup the breadboard to do some component validation.  I wired a relay, BC517, and 1M ohm resistor.  I then coupled it to an Arduino Uno.  I don’t remember what sketch is on the Uno, but when I put a wire to pin 1 the relay started going off like a door bell.  Good enough for testing.  After an hour or two I’ll have accumulated enough cycles.  It’s running at around 4 cycles a second.  That yields 14,400 cycles an hour.  I’ll let it go for a couple of hours.  28,800 cycles is a good break in test.

For your amusement I’ve attached a short video I took with my Nexus 4 Android phone.