IDC cable

[ahmedragia21]

Hi, i tried to connect an array of leds from a 5V source with the required leds , i used a one meter IDC cable 16 pins header , the voltage at the end of cable were 1.3V , huge voltage drop .. what should i do to correct this problem ? the resistance of the cable were 1.3 mega ohms as i measured ... i need a soultion to this problem please ..
thanks

 

[dknguyen]

Use thicker wire, less current, or check for bad high resistance connections.

 

[blueroomelectronics]

How large is the array, how many conductors is the IDC cable?

 

[ahmedragia21]

so better to use a normal wires than the IDC cables ? and solder the 16 pins wires ?

 

[blueroomelectronics]

Ok so it's 16 conductor IDC cable, how many LEDs?

 

[ahmedragia21]

blueroomelectronics, there are 16 Pins (conductors )
the array is just 6 LEDs , with 6 LDRs , much like the line follower array circuits

 

[dknguyen]

Well if the wire resistance is actually 1.3Mohms and you are sending 20mA through it for the LED that woudl make a voltage drop of 26kV. So either somethign is wrong with your measurements, or the cable.

You could try using just regular (thicker) two wires for all the LEDs (and each LED has it's own current limiting resistor). Also make sure your voltage source is strong enough since 20mA/LED with 6 LEDs is 120mA. Don't you need more than one wire per LDR? Unless you've connected things differently. I'm just pointing it out just in case.

 

[ahmedragia21]

what about using a cat5 cable ?
there are actually 6 LEDS/6LDRs , has common ground, each LED has its own current limiting resistor, on the cable its written 230V rating , also what about shorten the cable to half meter instead of 1 meter ?

 

[dknguyen]

Why bother using any fancy cat5 cables? I don't think they are designed to carry current. Just use normal thicker wire. A shorter cable (do you really need it to be 1m long?) would also reduce resistance definately. Cables should be as short as you can make them.

 

[ahmedragia21]

really im so lazy to solder 16 Wires of different color for 3 robots , that's why i used the IDC cables , yea the distance is about 1 meter ...

 

[3v0]

As others have pointed out that is way too much voltage drop. Take an ohm meter and check the cable for opens and more important shorts between hot and gnd pins. Most apt to be between wires adjacent each other on the cable.

It sounds simple but post a schematic just to be sure.

 

[Bob Scott]

really im so lazy to solder 16 Wires of different color for 3 robots , that's why i used the IDC cables , yea the distance is about 1 meter ...

Ribbon cable just about any length should be fine for LEDs in your robot. No need to shorten. Current carrying information is readily available on the net.

Look for a break in your wiring. Any reading above 10 ohms means you have bad wires.

Bob