Thursday, October 9, 2008

Home-made Double Layer ATmega32 PCB for RS232/RS422 Communication testing

Hi guys,
after making my single layer starter's kit M32_Card, I was looking for making a double layer M32 PCB at home. So, here is my attempt to make it. Well, it didn't turn out to be as difficult as I had thought it to be earlier. I had to dump one PCB before making this one as the top-layer routine was not solder-friendly!!

I've made this one mainly for an application where RS232 & RS422 testing was required. It uses MAX232 & MAX488 ICs from for those serial communication. Selection between RS232 & RS422 is through jumpers. The board is using ATmega32 controller, just like my single layer pcb. It also has 4x4 matrix keyboard, an LCD interface, ADC connector, SPI connector (for In System Programming), a reset switch and an LED for beginner's programming. It operates with the standard 12v DC adapter.

Here is the schematic (click on the image to enlarge):

There is a small mistake here in the schematic, the RX/TX pin connections in the RS232 connector are swapped, which I found while testing the PCB. So, I had to correct it by cutting those two tracks and placing jumpers. After the correction, the communication with PC was established. The schematic is similar to the M32_Card, accept that I've removed the RTC DS1307 and placed the MAX488. Also, the individual push buttons are replaced with the 16 key matrix key-board.
Click here to get more info and for downloading code to interface the 4x4 matrix keyboard shown here

The PCB etching is done with Ferric Chloride. In making the double layer PCB, as I don't have any PTH (printed through holes) facility, I've put small pieces of single core wire into the holes and soldered both sides. Check out the top and bottom layers here

If you have an application where the circuit can not be contained in a single layer, a home-made double layer PCB is worth a try!!



cahcyber said...

How to maintain for component that should be on Top Layer and which component should be on Bottom Layer?
I try to design it using Protel 99 SE, can I do that?
How to connect between Top Layer and Bottom Layer on Protel Schematic?

CC Dharmani said...

Hi, usually one side contains all the components and some tracks and other side contains only the tracks, as all the tracks can not be routed on one side due to higher density of tracks.
you can do the same in Protel also. You can use auto-routing, and it'll take care of the connections between two layers. when you give the layout for manufacturing, they'll make proper connections between two layer using PTH (Printed thru Holes)
If you are making the PCB at home, it would be advisable to first run the auto-router for bottom-layer and then whichever tracks remain unrouted, you can manually route them on the top layer. This way the complexity of the tracks will remain minimum on the top layer.
In home-made PCB, PTH will not be there, so you have to connect the two layers by passing small wires thru the holes and soldering them on both sides.

Harsh Shah said...

Hi sir,

I live in Ahmedabad (Gujarat - India). I saw in your profile that u live in chennai. My question is that from where did u get the 4x4 matrix keypad ? Because i have searched all electronic shops here in ahmedabad and i'm unable to find it. Do u know any shop in ahmedabad from where i can get it ?

CC Dharmani said...

Hi Harsh, in Ahmedabad also, you can get this keypad from the electronics market where they sell electronic components or telephone accessories, I don't remember the area name right now.
You can try at following address, they have the 4x4 keypad:

Sunrom Technologies
33, 1st Floor, Yash Niketan Complex
Opp. Khokhra Police Station
Khokhra Circle, Maninagar(East)
Ahmedabad - 380026
(item model No. 5000-0007)

Anonymous said...

Hi sir, please send me all the steps of protel design the single layer pcb and double layer pcb
because i want to learn that PROTEL DESIGN application