Pro mini undershield
I’ve designed another PCB 🙂 This time it’s a simple undershield for the Arduino pro mini. I received the PCB’s from Electrodragon (12$ for 10PCB’s) last week. The PCB has a Schottky diode and a 5V linear regulator, I’m using an LM2940 5V regulator. For the rest there are just 2 rows of female headers to plug the pro mini in and 3 rows of male pins on each side.
The reason I’ve had this PCB made is that pro mini’s are dirt cheap these days, you can find them on Ebay or Chinese shops for less then 4$. That makes them the cheapest Arduino on the internet. It’s cheaper and easier to buy a pro mini and integrate it in to your own project then to design your own PCB with an ATmega328.
The pro mini on its own is not very usable in projects. They were designed to plug in to a breadboard. With this undershield they are lot more usable. The pro mini only has a tiny 5V regulator, you can’t draw much current from it before it goes up in smoke. By using the undershield the pro mini is powered through the Vin pin, via a Schottky diode. The rows of 5V pins are powered from the LM2940 regulator.
BTW the pro mini does not have an USB to serial chip. So you need to have USB to serial cable to upload sketches to the pro mini. I use an FTDI cable. I’ve bought several pro mini’s on Ebay and none had a bootloader on them. Thankfully I have an USBasp to upload the bootloader via ISP. So you’ve been warned 🙂
Pro mini undershield
You can download the Eagle (7.3.0) files here.
Very nice idea and work – I am also playing a lot with these cheap pro minis board 🙂
Do you share your PCB source file somewhere ?
I’ll post the Eagle files when I have some time. Need to clean them up and put some kind of license on them. If you want a couple of PCB’s you can sent me some Euro’s to cover shipping and I’ll mail you the boards.
Hey there, id like to get a PCB too, how much would shipping be?
2€ for the EU, 4€ for the rest of the world.
Awesome! don’t have a paypal, any other way of getting it?
Sorry only paypal…
Ah well, time to get a paypal!
Okay, got one, going to need an email address to send money to
Sent me an email, info |at| bajdi d0t com
Done
Hi I came across this post quite by accident after searching for something similar. I was wondering would it be possible that I can maybe order ten of your PCBs.
Thank Andy.
Andy, sent me an email: info ]@[ bajdi dot com.
Hello, you mentioned that you were going to post the Eagle files for your “under shield” project. Have you had time to do that yet? If and when you do would you please let me know. I would like to use them to learn PCB prototyping and to modify them for a scratch build quadcopter project I am attempting.
Many Thanks and Best regards
Very nice PCB. I saw you have not included the A5,A5, A6 and A7 pins. Pins A4 and A5 are very important for I2C communication.
Maybe your next PCB revision includes these pins.
Correct, the problem is that there are different versions of the Pro Mini that have those analog pins in different places. I have a dozen Chinese Pro Mini clones with 3 different PCB layouts…
Yes, and in addition, expand the distance between the headers a bit, they are canted inwards when the pro mini is mounted on them
Any chance you can post your eagle drawing for the board you created, as you’d mentioned before.. I know not all boards are the same, but I can tweak the drawing as needed and I’m too far away to order a board from you… thanks!!! I know the Arduino community will love your contribution!
Hi, I have already sent an email. I have pro mini Atmega328 5v 16 mhz. I will be very thankful if you send me your eagle files for the board you have designed. I tried to use pro mini in my robotic car and its tiny regulator not good for all servos and other stuff.
Thanks
I’ve added a link to the Eagle files 🙂
i like to get a PCB too, how much would shipping be to lebanon if i buy 10pcs? I’m waiting your reply as soon as possible
I don’t sell any PCB’s. You can have your own made, just download the Eagle files and have them made at your favorite PCB manufacturer. I use dirtypcbs.com.
Hi, What are the values of capacitors?
Please can you post the specifications of the capacitors c1 , c2 and c3 and the schottky diode
I used a 1N5818 schottky diode. The value of the capacitors depends on the specifications of the regulator you use, look up the datasheet of the regulator you will use.
Thank you for making this design available. I have puchased 10 of your boards from DirtyPCB. Recommended. I am now building.
Thank you for details on the diode. The TI LM2940 5v spec sheet only specifies c1 and c2 (0.47uF and 22uF respectively) Are the details of c3 buried in the fine print of the spec sheet? Can I ignore it? Please advise.
C3 is not really necessary, I have a habit of putting a 0,1µF ceramic capacitor on the output of a voltage regulator.