– Copied from customer email –
We are using single color leds , that support 2v input. Our goal is to make them provide acceptable brightness and to make them blink.
Is there a way to connect a single color led and make it blink?
The forum post below provides useful context on how the LEDs work on UbiSwitch.
The LED lines are multiplexed, so one line does not correspond directly to one LED signal. The schematic below shows how they are connected.
The lines named on the connector are shown below.
EE_CLK_C0_LED_P1_LED0_FLOW = C0_LED (C0 printed on the board)
EE_DOUT_C1_LED_P6_LED0 = C1_LED
C2_LED_P7_LED0 = C2_LED
C3_LED_P8_LED0 = C3_LED
R0_LED_P1_LED0 = R0_LED
R1_LED_P2_LED0 = R1_LED
By connecting the Column lines (C0, C1, C2, C3) and Row lines (R0, R1) in specific ways, you can access the LED lines as needed.
The table below shows how the rows and columns correspond to different LED signals. Each port has two LED signals associated with it, one for activity, and one for link.
| C0_LED | C1_LED | C2_LED | C3_LED | |
|---|---|---|---|---|
| R0_LED | Port 1, LED0 | Port 1, LED 1 | Port 2, LED 0 | Port 2, LED 1 |
| R1_LED | Port 3, LED0 | Port 3, LED 1 | Port 4, LED 0 | Port 4, LED 1 |
LED 0
Off = No Link
On = 1000M link
Blink = 1000BASE-T activity
LED 1
Off = No Link
On = 10/100M link
Blink = 10/100 activity
These LED signals are designed for use with dual colour LEDs. This allows a single LED package to display both link speed information (with colour) and link activity information (off/on/blink).
To clarify how you connect an LED… For Port 1, 1000M link/activity LED, you would connect an LED between C0_LED (anode) and R0_LED (cathode).
If you are using a single colour LED, you would only be able to use either the 10/100M or the 1000M link/activity combination, which is not ideal.
You mention that your LEDs do not blink, and are always on. Please share your schematic for how you have connected your LEDs so we can check.
Regarding LED brightness, R4 and R5 (150 Ohm resistors) limit the current flowing in both the onboard LEDs, and your external LEDs. For your external LEDs, you can either add them directly on the LED header (in which case, the R4 and R5 will limit the current flowing through them), or you can add additional resistors in series with the external LEDs to reduce the brightness.
Note that the LED anodes (C0 to C3) are 3.3V level signals.
You should avoid modifying R4 and R5. Please note that modifying the board will void the warranty.
Added note…
The LED0 signals show link/activity for 1000M.
The LED1 signals show link/activity for 10/100M.
For reference, for port 1, 1000M, you should use…
Port 1 1000M Activity LED:
C0 (anode) ---------|>|----------- R0 (cathode)
– Copied from customer email –
We are about to order new batch of switches from you and led panels for these switches from other manufacturer,
We had some problem with getting our led panels to work properly and had to remove a resistor on the switch (and even though they worked, and blinked, the led couldn’t fully light, as if it was still missing power).
After which you suggested some other option for next batches to make the led after the resistor, but that would require us to add additional external resistor to avoid damage to the switch, however we’re so out of space in this product, even adding a resistor can be challenging.
Perhaps the easiest solution would be to keep the switch as is, and ask led panel manufacturer to change the leds instead.
Could you give us recommended specs of the leds we should use to get optimal results?
Or perhaps you can even suggest some specific part number that will work best with the switch?
These are the leds that were used last time, after resistor removal on the switch, green was still very dim , red was fine.
19-217/R6C-P1Q2/3T (red)
19-217/G7C-AL1M2B/3T (green)
Best way to analyse this issue is to look at the current flow, let’s go through that here.
The current flow between both D1 (internal LED on UbiSwitch Baseboard Mini) and the external LED is shared. If we assume both LEDs drop 2V, that’s a current of shared 8.67mA between both LEDs (calculation below). Or around 4.3mA per LED. This isn’t a lot of current.
I(resistor) = (Vsource - Vled) / 150
I(resistor) = (3.3 - 2) / 150 = 8.67mA
For the red LED you are using it has a forward current of 25mA and has a luminous intensity range between 45 to 112 mcd.
For the green LED you are using, it has a forward current of 25mA and a luminous intensity range between 11.5 to 28.5 mcd.
From all this information, we can see that the current will be quite low in the external LED (compared to the forward current). We can also see that the green LED itself has a lower brightness, even at the same current as the red LED. To solve this issue, there are a few approaches you can take.
Suggestion 1) Find a brighter green LED - You can use a green LED that has a higher brightness for the same forward current
Suggestion 2) Find a lower forward current green LED - You can find an LED that requires a lower current to achieve the same brightness (this is actually the same as suggestion 1).
Suggestion 3) Remove the LEDs on the UbiSwitch Baseboard Mini - If you’re not using the onboard LEDs on UbiSwitch BaseBoard Mini, you can just desolder them. This will mean all the available current will flow through your external LED. Probably this will solve your issue with your existing green LED. This is probably the best solution but remember, you will void the warranty if you modify our boards.
You’ll need to test and experiment with my suggestions above.
