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7 segment decoder

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Hello Sir,
I am using string of LED directly with 12V and 120Ohm via CD4511, the brightness very fine because of Oval leds.
 
Lets start again.... Forget any driver.... The schematics from the "TheLearningPit"... Are they what you need?

I think we have overstepped the mark on this one? Original post:-

R said:
Hello guys,
What to do for 7 segment decoder, actually i have done project with 7447 with small/ 1 chip red leds at 5v.
But now i have 5 leds in series with 120ohms.
How to decodes this voltage is at 12V .

All you really need to know is... Is it okay to drive 5 LED's per output on a 4511....
The 4511 can source 25mA so maybe you could drive them at 12v directly... I would still use the 120 ohm resistor..

I'm not quite sure if the 4511 can sink current... The datasheet say's that all input pins are maxed at 10mA...
 
Last edited:
Hello,
yes it is true! current per segment is ~6mA i have measured! in 5 string LEDs may some ore error in Digital multi meter may be.
 

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Hello,
The Vcc is 12.42 right now is adapter SMPS after that there will be transformer!
total current is 222mA for 0 in 4 digits!
the voltage across string is 9.96V, Vf of led is 1.92V, current per segment is 8.89mA and voltage across resistance is 1.8V.
 
Hello,
The Vcc is 12.42 right now is adapter SMPS after that there will be transformer!
total current is 222mA for 0 in 4 digits!
the voltage across string is 9.96V, Vf of led is 1.92V, current per segment is 8.89mA and voltage across resistance is 1.8V.
So what's your problem? All the criteria seems to be met... If it works what is the issue..
 
Here is the circuit only Vcc at 12V, and input with pull down of 10k and input of 9.4K same!
One thing more the input wire i have is cable of 5 wires. in circular color coded (I don't know the Name)
what will be the maximum length of input wire to work on it?
 

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You multimeter most likely has a series resistor like 10 or 100 ohms when measuring current. That's why we asked for th voltage across your resistor rto get current.
 
You multimeter most likely has a series resistor like 10 or 100 ohms when measuring current. That's why we asked for th voltage across your resistor rto get current.
I HAVE POSTED ALL INFO.
The Vcc is 12.42 right now is adapter SMPS after that there will be transformer!
total current is 222mA for 0 in 4 digits!
the voltage across string is 9.96V, Vf of led is 1.92V, current per segment is 8.89mA and voltage across resistance is 1.8V.
 
Hello,
There is some problem as THE PLC work in 24V and this circuit at 12V.
The Input are connected to Gnd with pull down of 10K, when the inputis connected to 12V it work as BCD 8421 on display.
But when i use external 24V the Gnd of both are common and the 24 to input the signal does not work well.
how to connect both of PLC 24 nad internal 12V led display together
 
I HAVE POSTED ALL INFO.
The Vcc is 12.42 right now is adapter SMPS after that there will be transformer!
total current is 222mA for 0 in 4 digits!
the voltage across string is 9.96V, Vf of led is 1.92V, current per segment is 8.89mA and voltage across resistance is 1.8V.

Why is there a transformer after the SMPS? IF the SMPS output is 12.42VDC, and the other numbers you report are all correct and prevail across all operating modes, then there is no need for a transformer, nor would one do anything for you, as DC won't go through a transformer.
 
Hello,
There is some problem as THE PLC work in 24V and this circuit at 12V.
The Input are connected to Gnd with pull down of 10K, when the inputis connected to 12V it work as BCD 8421 on display.
But when i use external 24V the Gnd of both are common and the 24 to input the signal does not work well.
how to connect both of PLC 24 nad internal 12V led display together

You can divide the 24V from the PLC to the 12V you need fro the decoder with a series pair of 10K resistors on each line.
Code:
(24V PLC)
|
[10k]
|
(tap to 12V decoder)
|
[10k]
|
(common gnd)
 
mtr = meters as opposed to feet.

The logic supply has to stay within the logic supply range. If your feeding 24 V to the inputs of the 4511 expect smoke.

You CAN communicate from the PLC with open collector outputs, but the inputs of the 4511 would be pulled up to the logic supply of the 4511 which is 12 V. You then have to pull the inputs to ground with the PLC, but now they are inverted.

You also have to watch when different systems are unpowered when you don't pull inputs to ground.
 
Why is there a transformer after the SMPS? IF the SMPS output is 12.42VDC, and the other numbers you report are all correct and prevail across all operating modes, then there is no need for a transformer, nor would one do anything for you, as DC won't go through a transformer.
Hello,
It is only 12V, never mind the SMPS and transformer.

You CAN communicate from the PLC
i have no idea of CAN.
 
You can divide the 24V from the PLC to the 12V you need fro the decoder with a series pair of 10K resistors on each line.
Code:
(24V PLC)
|
[10k]
|
(tap to 12V decoder)
|
[10k]
|
(common gnd)
Hello,I am using 24V supply here in industry there will be 24V operated PLC.
so, when i use 4.7K 4.7K voltage divider in place of 10K.
it give 12V and after this the GND of both common, the 12V from 24V divider feed to input of CD4511 it is not working still!
 
The logic supply has to stay within the logic supply range. If your feeding 24 V to the inputs of the 4511 expect smoke.
Yes, I know...
Here is schematic
 

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Yes, I know...
Here is schematic
Hoorayyy!!!

If you want to use 24v and 12v use zener diodes on the inputs... If you use a 2k2 resistor with a 5v1 zener then it should work with 24v input and 12v input..
 
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