Peripheral Devices That I have but Don't know how to use. Help Please.

Adding to the list of Devices that I can't use is an IC 7 Segment display Decoder (http://www.jaycar.com.au/products_uploaded/ZC4511.pdf).  I can wire the corresponding letters to the corresponding segments but I don't understand what some of the pins are:

1. LE

2. LT

3. BT

On the Display itself, it has a pin marked Dp which I guess is the backlight.  Where does this go on the IC?

And it is a Common Cathode Display (I checked).

Thanks in advance.

Fergus Byrne wrote:

 

Adding to the list of Devices that I can't use is an IC 7 Segment display Decoder (http://www.jaycar.com.au/products_uploaded/ZC4511.pdf).  I can wire the corresponding letters to the corresponding segments but I don't understand what some of the pins are:

1. LE

2. LT

3. BT

 

 

On the Display itself, it has a pin marked Dp which I guess is the backlight.  Where does this go on the IC?

 

And it is a Common Cathode Display (I checked).

 

Thanks in advance.

The CD4511 data sheet describes ~LT, ~Bl, and LE in text and in the truth table.  ~LT is "Lamp Test" and when low turns on all segments.  ~LT has priority over all other inputs.  ~Bl is "Blanking" and when low turns all segments off, assuming ~LT is high = inactive.  ~Bl is used to blank the display to save power or can control brightness using pulse width modulation, i.e., with a variable duty cycle.  It has priority over LE.  LE is "Latch Enable" and when high stores the DCBA input that was present when LE rose from 0 to 1.  If LE = 0, the latch is transparent and segments a-g follow DCBA.  If LE = 1, the CD4511 ignores the DCBA inputs and displays the stored DCBA value.  LE is useful if you want to drive multiple digits from RasPi's limited GPIO signals since you can share the DCBA signals and provide a separate LE for each digit.

CD4511 a-g outputs are active high and need to be used with a common cathode LED array.

The decimal point DP is not controlled by the CD4511 and if used must be driven with other circuits.

I have now wired the chip as per the specifications above ^.

Can someone please check my code and tell me why it won't work please.

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BOARD)

GPIO.setup(7, GPIO.OUT)

GPIO.setup(11, GPIO.OUT)

GPIO.setup(12, GPIO.OUT)

GPIO.setup(13, GPIO.OUT)

 

 

# 7 = Decoder A   2^0 = 1

# 11 = Decoder B  2^1 = 2

# 12 = Decoder C  2^2 = 4

# 13 = Decoder D  2^3 = 8

 

 

i = input("Enter the Number 0 - 9: ")

while i!="":

          if i=="0":

                    GPIO.output(7, GPIO.HIGH)

                    GPIO.output(11, GPIO.HIGH)

                    GPIO.output(12, GPIO.HIGH)

                    GPIO.output(13, GPIO.HIGH)

          elif i=="1":

                    GPIO.output(7, GPIO.LOW)

                    GPIO.output(11, GPIO.HIGH)

                    GPIO.output(12, GPIO.HIGH)

                    GPIO.output(13, GPIO.HIGH)

          elif i=="2":

                    GPIO.output(7, GPIO.HIGH)

                    GPIO.output(11, GPIO.LOW)

                    GPIO.output(12, GPIO.HIGH)

                    GPIO.output(13, GPIO.LOW)

          elif i=="3":

                    GPIO.output(7, GPIO.LOW)

                    GPIO.output(11, GPIO.HIGH)

                    GPIO.output(12, GPIO.HIGH)

                    GPIO.output(13, GPIO.HIGH)

          elif i=="4":

                    GPIO.output(7, GPIO.HIGH)

                    GPIO.output(11, GPIO.HIGH)

                    GPIO.output(12, GPIO.LOW)

                    GPIO.output(13, GPIO.HIGH)

          elif i=="5":

                    GPIO.output(7, GPIO.LOW)

                    GPIO.output(11, GPIO.HIGH)

                    GPIO.output(12, GPIO.LOW)

                    GPIO.output(13, GPIO.HIGH)

          elif i=="6":

                    GPIO.output(7, GPIO.HIGH)

                    GPIO.output(11, GPIO.LOW)

                    GPIO.output(12, GPIO.LOW)

                    GPIO.output(13, GPIO.HIGH)

          elif i=="7":

                    GPIO.output(7, GPIO.LOW)

                    GPIO.output(11, GPIO.LOW)

                    GPIO.output(12, GPIO.LOW)

                    GPIO.output(13, GPIO.HIGH)

          elif i=="8":

                    GPIO.output(7, GPIO.HIGH)

                    GPIO.output(11, GPIO.HIGH)

                    GPIO.output(12, GPIO.HIGH)

                    GPIO.output(13, GPIO.LOW)

          elif i=="9":

                    GPIO.output(7, GPIO.LOW)

                    GPIO.output(11, GPIO.HIGH)

                    GPIO.output(12, GPIO.HIGH)

                    GPIO.output(13, GPIO.LOW)

          else:

                    print "You didn't enter a valid number!"

 

          i = input("Enter the Number 0 - 9: ")

if: i == "":

          print "Closing application..."

It just skips to the else statement with in the while statement. here the statements are not nested but in my code, they are nested.

Bit of a mess but here is a schematic of what I have wired up.  Last night, I had power going into the DP and a little light came on but today that is not happening.  Have I blown the chip?

>  i = input("Enter the Number 0 - 9: ")

I think you want raw_intput instead of input.

The difference is that input accepts commands and tries to evaluate them,

which probably isn't what you want, although it wouldn't matter if the user

just types digits.

> if i=="0":

I don't think you want the quotes around 0, since the variable i

holds an integer.  The input function automatically converts to integer

when it can.

In case 2, output 13 should be high.

In case 3, output 11 should be low.

What about the wiring above?  Is it good?

it doesn't have any obvious flaws.

I'm not qualified to find any subtle flaws.

Fergus Byrne wrote:

 

Bit of a mess but here is a schematic of what I have wired up.  Last night, I had power going into the DP and a little light came on but today that is not happening.  Have I blown the chip?

I don't see any current limiting resistors in your diagram.  Typical LEDs use 1.6V (red) to 2.4V (green).  If you put 3.3V across them without current limiting they will emit a lot of light -- once.  Then they'll be DED.  Driving one directly from a RasPi BCM2835 output without current limit could also damage the BCM2835 output.

I just checked Wikipedia.  They have a thorough article on LEDs and also one that shows how to power an LED using a current limiting resistor and how to calculate its value.  Typical values are 150 Ohm to 1K Ohm depending on the driver voltage, the LED's efficiency and how bright you want it to be.

So you think I have "blown the bolb" on the 7 segment display?  If so, that would mean that the IC is still in place and I can get up and running when I get a new 7 segment dispaly...Right?

Fergus Byrne wrote:

 

So you think I have "blown the bolb" on the 7 segment display?  If so, that would mean that the IC is still in place and I can get up and running when I get a new 7 segment dispaly...Right?

You've probably only destroyed the DP LED.  If you didn't see a bright flash from the other segments, they're probably still intact.  It all depends on what the CD4511 DCBA inputs were when you powered it on.  If DCBA are 1010 through 1111 then outputs a-g are low and the LEDs aren't driven.  With the CD4511 disconnected, try powerering each LED segment from +3.3V through a 150-300 Ohm resistor and see which ones still light up.

You could test your display by using the diode test setting on a multimeter.

If your meter is digital, the negative lead goes to the CC connection and then one by one place the positive lead on the segment pins, each segment will light. Possibly very faintly, depends on the actual display involved.

If your meter is an analogue one (it has a needle meter), then you might need to reverse the connections above. The meter is unlikely to give more than 2v and will be low current.

Will look into it when I get back from holidays.  Thanks for responce.

Will look into it when I get back from holidays.  Thanks for responce.