External Led's

Hello everyone,

When my board will arrive, i plan to mount external LED’s in the housing.

The reason is that i cannot identify which of the 2 PCB mounted LED’s behind each other is active when i just make holes in the housing front where the PCB mounted LED’s are (both are dual colour LED’s).

Can i use the following LED’s for that?

I don’t find more details when i look in the user manual on 3.4.4 Indication LEDs

Regards Ben

Hi @pe2ben,

LEDs from your link should be OK. You have to remove SMD LEDs (LED1, LED2, LED7, LED8) from the LimeSDR-USB board when soldering thru hole version (LED3, LED4, LED5, LED6).

As a side note - you may use LED standoffs for thru hole LEDs. We tested this set:

  1. Standoff
  2. LED

By the way, LEDs from your ebay link will not fit to the standoff listed above.

I plan to use this LED’s: http://www.conrad.com/ce/en/product/1126622/?insert=62&insertNoDeeplink&productname=LED-Baustein-Gruen-Rot-L-x-B-x-H-1333-x-1166-x-508-mm-Dialight-553-0711-300F

73 de Sabine, OE1YVW

Hallo Sabine,

In my opinion these LED’s are not correct.
You need Bi color LED’s with 2 pole’s.

See my Ebay link or the link from Zack (LED).
This is because the LED’s can be programmed for red or green.
Look at this part of the schematics where you can see that the LED have 2 colors depending from the current direction (for instance LED1 G(reen) and LED1 R(ed)) :

Gruß Ben 73.

Hello Zack,

Thanks again.

Do i really have to remove the SMD LED’s or would otherwise the current to high for the FPGA I/O port (max I OUT DC output current, per pin 40 mA) ?
Do you know how much the maximum current is in both directions from the dual color SMD LED’s ?

Regards Ben

I don’t like doing anything with SMD parts. So I will use a light pipe.


You may be able to salvage some from other devices too.

1 Like

I never used these ones.
But is the lens not to big for the SMD LED’s?
How can i bend and fix this tubes?
Regards Ben

You can check the measurements of the LED and get a light pipe that is suitable. The lens as you call it is the indicator for that link. There is also jacketed optic cable for sale. Real optic cable has low loss.

Hello Ben!

The LED’s I choose are Bi Color Led. You can see that in the datasheet http://www.produktinfo.conrad.com/datenblaetter/1100000-1199999/001126622-da-01-en-LED_2HI_3MM_ROT_GRN_553_0711_300F_DIA.pdf (Part No. 553-0711-300).

Hallo Sabine,

Ok, I see it: Type 7 ones.
Also they are diffuse ones (just 10 mA).
I wait for a answer from Zack (regarding the current from the SMD LED’s and max. current I/O ports) if it is possible to use it in combination with them.
If not, i will look for the solution from hTo137.

Regards Ben

Hi @pe2ben,
Well, the LED circuitry was designed for SMD or TH LEDs i.e. there is only one resistor. So, there is a possibility that LEDs will not lit equally or one LED may not lit at all.
The correct way would be remove SMD diodes if you use TH. But TH should work with SMD as well, just have in mind what is said above.

BTW the LED’s from Conrad I’m using needs a little modification, as red and green are reversed:
bend the connectors up, push the LED’s out to the front, turn them 180° and then back in.

Regards and 73, Sabine, OE1YVW

I used the LED’s from the BOM. Did not remove the SMD ones. So far, seems to work 100% through hours of testing…


Love that case

Do you find that the red and green are approximately equal in brightness? I was searching DigiKey for bicolor LED’s and came across these:


The red and green sides are both 2.1 volts and 10 ma and supposedly equal brightness. I think that the lower current requirement is a plus (10 ma instead of 20 ma) but then I wonder if I would need to insert additional resistors to compensate for that. I suppose at $0.93 each I could afford to buy both the specified LED’s and these and experiment with them…

They seem to be pretty equal to me. Connections were straight to the board. No additional resistors used.