7 segment display: 4511B or 4026B?

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Benjie

Senior Member
dear forum,

I intend to replace a working LCD display with three 7 segment displays.
In the forum I noticed that most of people uses the 4511B while the interface manual describe a simple code and simpler cascading using the 4026B.
I have a manual rotary encoder which transitions are counted by a 20X1 with a maximum count of 128. At 128 the display will be scaled-up to show 16.0 (fixed point).

Which of the two circuit is the most suited for such task?

Thanks
 
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PaulRB

Senior Member
Benjie, can you say a little more what the circuit is doing?

For 3 digits, you will need either 3 x 4511B or 3 x 4026B.

The 4026 is also a counter, and I think it will only count up. So if you turn your rotary encoder down, do you need the number displayed to also go down? If so, with the 4026, you will have to reset the counters and then re-send pulses to display one number less than before. The counters can be connected in series, so you will only need to use 2 output pins from the picaxe, one for sending pulses to be counted, and one to reset all three counter chips.

There is a similar chip - 4029 - which can count up or down.

The 4511 is a latch. You will need 4 pins from the picaxe to send data to a single digit, and one pin to latch the data per chip, so 7 pins in total. Counting up or down must be done by the picaxe.

None of these chips can provide very much current to the display. How bright to you need?

Another chip to consider would be the max7219. I have been using these recently. You will only need one chip to drive from 1 up to 8 digit displays. Very simple to wire up - only one extra resistor needed. 3 pins from the picaxe needed to control the chip. You can adjust the brightness, and it will be very bright if you want.

Paul
 
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Benjie

Senior Member
Thank you Westaus55 and PaulRB for the alternative solution that I will investigate with attention. The 4026B will be discarded because it cannot count up and down, i will consider the other chips.
In respons to Jim Perry: I want to replace the 2 lines LCD because the length of the code driving it which slow down the operation, secondly because the digits are small.
The application is a radio controlled (433 MHz) antenna tuner for radio amateur applications.

Thanks to all.
 
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westaust55

Moderator
If you currently have the LCD connected using a parallel interface with 6 or more outputs required which will take program space and time, then you could consider creating a serial to parallel adapter with either:
1. the Rev Ed FRM010 serial to LCD chip - http://www.techsupplies.co.uk/epages/Store.sf/en_GB/?ObjectPath=/Shops/Store.TechSupplies/Products/FRM010
2. A second PICAXE chip used as a serial to parallel LCD interface. Ron Hackett in his book and several past threads here have used that approach.

Either of these solutions allow the primary PICAXE chip to send commands easily using the SEROUT command and a single output pin.
 
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