My first Arduino shield for the MLX90620/21

Im about 1 week away from sending my first Arduino UNO based shield design to be manufactured.
I wanted to get a little input from the group.

As you can see from the attachments the main sensor is a 16x4 pixel thermal imager (MLX90620/21)
I have tested it on breadboard and the results are “ballpark” except for the 90621 which is ~10F off from the 90620
Im working with the coder who converted someone else’s code from a different library

I have also thrown in an I2C bus buffer and the pullups (for an external are set for a 20M cable. I have created a quick and dirty
based application to parse and display the data. There is also a 1wire local and remote bus with an extension connector.

Its a 4 layer board and 1 SDA and 1 SCL line do cross at layer 1 and layer 4, Im thinking that should not be a problem
because of the low speed … at least I think so …

Let me know your first impressions!


Hi Mike At a quick glance, Why use a 4layer for a simple project I know most people would say it's better but unless it's absolutely critical I would not go down this route for this design. Don't mean to be rude but looking at your PCB it looks a bit messy to the eye and the tracks are not laid out correctly. You should avoid 90DEg corners and always come from the enter of the pad. Here is a good guide and some PCB design techniques links I found useful.

like I said I've only had a quick glance at it makes it a bit harder when you cannot see the ground/power planes what PCB software did you design it in ? PCB design is a black art and takes years of practice, I'm no expert myself but I like the finished product to be appealing to the eye as well as the rule of thumb laid out correctly depending on the design like digital and high speed signal's and to help EMC and signal integrity.


Thanks for the input. I am using ExpressPCB for both the schematic capture and PCB layout. No I do not think your being rude, this is good information, Ill take a look at your links.

I had some input from another site that suggested I should make it Arduino R1 R2 and R3 compatable so I modified the board. Thanks

Hi, 4 layer???

I see a yellow overlay, red top layer, green bottom layer, a 2 layer PCB. I'd make the tracks a bit wider and the doughnuts a bit thicker, you will be hand soldering to these, possibly resoldering too.

Tom.... :)