president madison green display

[bioman]

my madison has a dead segment in the display LED so i plan to replace it with a green one to match the clock

will i need to change the resistors on the board to be combatible with a green display since it currently has a red one in it/?

i know the regular green 5MM LED lights want 2.2V but am not sure aboiut the displays and id hate to ruin the new one

thanx
scott

 

[formulamojo]

I wouldn't think so. The resistors have no way of knowing what color the display is. As long as the new display is a drop in replacement for the old it should work.

 

[bioman]

i see what you mean

i had thought that maybe green LEDs would want a different voltage than the red ones .....

changing the resistors to a different value would give a different voltage correct?

 

[formulamojo]

Yes. A larger resistor would drop more voltage across it there for affecting the final voltage of the circuit. Not enough to be noticable unless a large change was made to the resistor.

For example I was experimenting with my 13.8V power supply and a diode trying to dim it. when i put a 50 ohm resistor in series with the diode it only dropped the voltage going to the diode to 13.7V. A tenth of a volt wasn't noticed in my experiment, but it gave me a base line to work with. I now know that i need a 500 ohm or greater resistor to drop my voltage by 1 volt.

 

[bioman]

ok so it shouldnt make a difference in spots where a LED already was such as on the channel display and and the lights for AM/LLSB etc.....

i know i will need resistors where i replace the 12V bulbs behind the meters to make them light up green as well but i DO have a calculator for that so i'm good there

i have the LEDs and the display just need to stop at rat shack on the way home to get the resistors i'll need to run 2 LEDs in series where there WAS 12V bulbs

i'll put up pics after is done

thanx for the help

scott

 

[formulamojo]

Have fun.

 

[loosecannon]

formulamojo,

the reason that resistor in series with the power supply only dropped the voltage by .1 volts is because you did not have a load on the supply.
that series resistor will act very differently when a load is applied.
(resistor placed across positive and negative)
LC

 

[formulamojo]

formulamojo,

the reason that resistor in series with the power supply only dropped the voltage by .1 volts is because you did not have a load on the supply.
that series resistor will act very differently when a load is applied.
(resistor placed across positive and negative)
LC

I know, I was trying to explain voltage drop to him. To answer his question.

They did teach me a thing or two in college where I earned a degree in electronics, But a newbie doesn't want to be bored with theory.

 

[TonyV225]

I believe they sell kits for these.

 

[bioman]

the "kit" comes with the display and one LED

i needed the display and 4 LEDs for AM/LSB/USB/CHAN9 on the madison PLUS i wanted to put green lights on the meters

the channel display is in and looking nice i just need to wire the LEDs for the meters and it is done but alas i leave for work momentarily

 

[74IN]

http://www.ledsupply.com/reca.php

 

[bioman]

thanx 74 ......

i already have a calc for the resistors and plan to pic them up at radio shack on the way home.....

now if i could just find a clock motor for that radio.....

 

[bioman]

ok after playing around with a bunch of resistors i had got from radio shack and some more out of my "parts" bin i just couldnt find the level of "brightness" i was looking for so i ended up tying the ground and the 15.2V sources from the original 2 lights together in parallel and ran 6LEDs in series .....PERFECT!!

i set them up in a triangle behind each meter so ive goot a nice green glow coming off of each one

after it gets dark ill take some pics and throw them up

scott

 

[formulamojo]

Nice.

 

[bioman]

as promised pics of the green

pics came out kind of crappy.... with the flash it was too bright and without was too dark and i havent really figured out how to operate this camera yet

everything came out nice and bright with the exception of the lights behind the clock....

IF i keep the clock in it i may end up going to white LEDs behind it since the light has to filter behind green numbers

the clock in it does not work <needs a motor> and if i cant find a motor for it i think i'm going to tear down a freq counter and install that in the window..... a green LED one of course

scott