Problem for interfacing 4 " Common Cathode 7 Segment Display with Arduino ....

Thread Starter

arjunvs626

Joined Nov 20, 2017
9
I have a 4 inch Common Cathode 7 Segment display and i don't know how to interface large size common cathode Seven segment displays . I am searched about this but most of them saying that In large digit common anode is best But The problem is i already bought 9 nos of Common Cathode display Please Help
 

jayanthd

Joined Jul 4, 2015
944
I have a 4 inch Common Cathode 7 Segment display and i don't know how to interface large size common cathode Seven segment displays . I am searched about this but most of them saying that In large digit common anode is best But The problem is i already bought 9 nos of Common Cathode display Please Help
Do you have the datasheet of the display ?

Is it suberbright display ?

You have to mention the max current requirement of each segment. All segments will draw equal amount of current. That is each display has 7 segments plus dot segment. All 7 segments draw same amount of current. dot segment draws a little less current. Mention the current drawn by one segment.

Based on that circuit has to be designed to drive it that is choosing the power transistor or better to use Mosfets.
 

Thread Starter

arjunvs626

Joined Nov 20, 2017
9
Do you have the datasheet of the display ?

Is it suberbright display ?

You have to mention the max current requirement of each segment. All segments will draw equal amount of current. That is each display has 7 segments plus dot segment. All 7 segments draw same amount of current. dot segment draws a little less current. Mention the current drawn by one segment.

Based on that circuit has to be designed to drive it that is choosing the power transistor or better to use Mosfets.
First of all thank you for replying Sir Its in its datasheet its 120ma

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jayanthd

Joined Jul 4, 2015
944
First of all thank you for replying Sir Its in its datasheet its 120ma
Ok. Then If all segments turn on at the same time then it is 120 ms * 8 = 960 mA. You can take it as 1A approx. So, you can use 4A type NPN transistors or N-Channel Mosfets of the same current rating that is 4A or more.

If needed I can provide you a circuit to drive the displays.

BD677 NPN transistors can be used or you can use IRPF054N N-Channel Mosfets.
 

Thread Starter

arjunvs626

Joined Nov 20, 2017
9
Ok. Then If all segments turn on at the same time then it is 120 ms * 8 = 960 mA. You can take it as 1A approx. So, you can use 4A type NPN transistors or N-Channel Mosfets of the same current rating that is 4A or more.

If needed I can provide you a circuit to drive the displays.

BD677 NPN transistors can be used or you can use IRPF054N N-Channel Mosfets.
Is 2n3904 can drive this one ??
 

jayanthd

Joined Jul 4, 2015
944
No, 2N3094 cannot drive it.

Wait, let me think a little. For driving the common cathode pin you can use 2A or 4A type Power transistor or N-Channel Mosfets that I mentioned but for connecting the 8 anode pins to microcontroller you need additional low power tarnsistors or mosfets because microcontroller pins cannot source or sink more than 25 mA current (for PIC) and 40 ma (for AVR).

Which MCU do you plan to use ?

PNP transistors have to be used to drive the 8 anode pins. You can use 8x BC328 transistors or any 500mA or more continuous collector or drain current handling PNP transistor or mosfets.
 

Thread Starter

arjunvs626

Joined Nov 20, 2017
9
No, 2N3094 cannot drive it.

Wait, let me think a little. For driving the common cathode pin you can use 2A or 4A type Power transistor or N-Channel Mosfets that I mentioned but for connecting the 8 anode pins to microcontroller you need additional low power tarnsistors or mosfets because microcontroller pins cannot source or sink more than 25 mA current (for PIC) and 40 ma (for AVR).

Which MCU do you plan to use ?

PNP transistors have to be used to drive the 8 anode pins. You can use 8x BC328 transistors or any 500mA or more continuous collector or drain current handling PNP transistor or mosfets.
k sir Then you said that BC328 is suitable for this
 

jayanthd

Joined Jul 4, 2015
944
k sir Then you said that BC328 is suitable for this
Yes, but do you have a code ?

BC328 is for driving the 8x anodes. For driving the common cathode pin you need 2A or 4A type NPN transistor or N-Channel Mosfet.

Total you need 8x BC328 and as many 2A say 40V NPN transistors or N-Channel Mosfets as you have displays. If you have 4 displays as you say then you need 4x 2A 40V NPN transistors or N-Channel Mosfets.

If you want circuit then I can provide it. I guess small change to code has to be done also. I have to admit that I have never used big 7 Segment displays.
 

Thread Starter

arjunvs626

Joined Nov 20, 2017
9
Yes, but do you have a code ?

BC328 is for driving the 8x anodes. For driving the common cathode pin you need 2A or 4A type NPN transistor or N-Channel Mosfet.

Total you need 8x BC328 and as many 2A say 40V NPN transistors or N-Channel Mosfets as you have displays. If you have 4 displays as you say then you need 4x 2A 40V NPN transistors or N-Channel Mosfets.

If you want circuit then I can provide it. I guess small change to code has to be done also. I have to admit that I have never used big 7 Segment displays.
K sir actually i have a code also send your code i will send my code to you my Email id is arjuntechnics@gmail.com
 

jayanthd

Joined Jul 4, 2015
944
ULNxxxx is not suitable. They have a 500mA per channel and they are NPN darlingtons and hence they can't replace the 8x PNP transistors and they cannot be used for driving common cathode pins because due to high current of 1A per SSD the ULNxxxx chip will heat up.
 

Thread Starter

arjunvs626

Joined Nov 20, 2017
9
ULNxxxx is not suitable. They have a 500mA per channel and they are NPN darlingtons and hence they can't replace the 8x PNP transistors and they cannot be used for driving common cathode pins because due to high current of 1A per SSD the ULNxxxx chip will heat up.
k sir now i am doing with bc328
 
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