Replacing 0.56" seven segment display?.

[Mark Snape]

Replacing 0.56" seven segment displays with Kingbright SA23-12SRWA?.

Dear All,

I wish to change the attached circuit to accept the larger Kingbright displays as this circuit only drives smaller 0.56" common anode types, could you please advise me what type of circuit i would need.



( Although the drawing does not actually show it the supply to the displays is currently +5volts and as the SA23 series contains more LEDS per segment i'm assuming the supply volts will need to be higher and i think that might then create a problem form the driving logic. But the 74LS47 used for the segment drive i think should be up to the task )



Many Thanks,
Mark Snape.

 

[k7elp60]

It will be a major problem, as the existing displays are multplexed and the common anode voltage is 5V. The new displays(SA23-12SRWA) need approximately 12V for the common anode voltage. The cathode drive circuits should be fine.

 

[Mark Snape]

Many Thanks for taking the time to respond, but isn't that the question
i was asking?.

Cheers,
Mark.

 

[JimB]

I looked at the datasheets for the new LEDS when you first started this thread and then forgot to compose a reply!

The new 7seg LEDS are pin compatible with the existing ones but will require a higher supply voltage.
The 74ls47 appears to be rated up to 15volts on the open collector drive to the leds, so I think that a 12v LED supply should be OK.

JimB

 

[Mark Snape]

Many Thanks JimB.

But it's how to translate the +5v o/p of the 'HC154 to drive the SA23-12SRWA
seven segment displays?.

Cheers,
Mark.

 

[JimB]

But it's how to translate the +5v o/p of the 'HC154 to drive the SA23-12SRWA
seven segment displays?.

Now that comes into the category of "Oh, I never thought of that!".

I think that a 7.5v zener diode between the outputs of the HC154 and the corresponding 2.2k resistors should fix the problem.
Connect the anodes of the zeners to the HC154.

JimB