Working but not working with cable- Help Plz

Dear friends, I had previously posted regarding my aquarium controller for two tanks. Basically used 1 Arduino Dem., to control all the outs for both the tanks. I made two control boxes, and the main control box has the keypad and LCD and the Arduino. The secondary control box has the outlets for the second tank and display of the parameters for the 2nd tank.

The main control and secondary control are connected with the help of a 25pin DB (male on the main control and female pin on the Secondary) after connecting them with the market-available 25pin cable, i found with the help of this forum that the market-cables-all 25pins are not connected. And i ended up making my own 25pin cable.

actually i am using only 6 wires in the 25, 2 for the + and Gnd, 2 for the SCL and SDA and 2 for the temperature sensors.

I am having this unique problem: When i connect the male of the main box and the female of the secondary box directly both of them work perfectly. When i connect using the cable (made by me), the main totally doesnt turn ON whereas the Secondary backlights ON but no characters on it...

Checked the Cable before powering the system up, the pins were not shorted.

When checked after powered, the pins are shorted, being the + with the SCL and, + with the Gnd and + with the SDA!!!...

When i remove the cable, get the female and male plugged in directly, they work perfectly...!!!!

I am powering the system using the USB from my computer...

the cable that connects both the system is 2meters in length.

Kindly help me out... changed the cable a zillion times, along with the 25pin DB Pins ... been soldering them for the last 1wk!!! but no luck!! same problem...

should i try it with the external power supply?

kindly advice what the problem might me.. a solution would be great.

Regards Peri

In wiring your cable are you sure your connecting the correct connector pin numbers together, pin 1 to pin 1, etc? It's easy to get mixed up and wire them as mirror images. The fact that boxes work when connected directly with the connectors, but doesn't work with your homemade cable kind of isolates it to cable wiring mix up. I know that's probably not what you want to hear after all the hours of troubleshooting the cables, but that's what it seems to an independent person, me. ;)

Hang in there, it is solvable. ;)


the way i soldered my cable is:

  1. connected the wire's female to the male of the main box- and then soldered the wires to the pins where they are... then
  2. connected the wire's male to the female of teh secondary box - and then soldered the wires to the pins where they are...

thats why i am not sure where the error is!!!...

Peri, I am sorry Lefty is right you have wired it up wrong. I don't understand your explanation of why you think you couldn't possibly be wrong. But as a general point when faced with a problem in electronics it always turns out to be the thing that couldn't possibly be wrong.

Face it, it works with a ready made cable but not with your home made one. So what is there not to say it is your cable.

Get your multi meter and measure the continuity of the wires between your cable and compare it with the ready made one. Make sure the correct connectors connect up on each cable.