Filed under: clock development protocircuit
The four inputs a, b, c and d on the 4511 connect to ground via four black cables (these can be seen in the previous entry) this gives the inputs a low reading. When these cables were removed the voltage pulls up through the 10k resister to the 4.5v and gives a high reading (1). Using these cables I was able to work out using a truth table how to count 0 to 9.
Filed under: clock development protocircuit
This protocircuit setup has moved on from the last protocircuit. On the previous circuit I was able to display three digits and count 0 to 9. The problem I had with this circuit was the numbers were not being displayed clearly. Other LED’s were lighting up causing the display to read unclear numbers. This is due to the electrons building up at the field effect transistor. This can be rectified by using 10k pull up resistors.
On this protocircuit I have used 10K pull up resistors on each of the inputs to the 4511 BCD. This enables the electrons that have not past through the field effect transistor to pass up through the 10K resistors. When the voltage to the inputs is connected to ground it give no pulse (0), when the connection to ground is disconnected it pulls up through the 10K resistors to the 4.5v giving the inputs on the 4511 a positive charge (1). This gives a much clearer display of the numbers.
Filed under: clock development protocircuit
In order to fault find, I have used a digital multimeter. Some of the digits on the display are not working. I used the multimeter to locate where there was a break in the protocircuit; this was stopping the voltage getting to one digit on the display. I also had some resistors with both legs on the same copper track on the protocircuit; this resulted in the resistor being bypassed and having no effect.
Filed under: clock development protocircuit
Initially the aim is to just get some numbers displayed on the four digit seven segment display. Using the circuit diagram from circuit wizard I was able to setup this protocircuit (See link for more info on protoboard). I also used the data-sheet for the four digit seven seg display. This enabled me to identify what each of the 12 pins on the display do. Using this data-sheet and the information I already had I was able to calculate what resistors were required between the seven pins from the 4511 and the seven pins on the display.
Calculations for Resistors.
IF=20ma Max Voltage 2.5 V/I = R 2.0/0.02= 1oo ohms resistor.
There is a 10% forgivness with this sum, so I selected 120ma resistors between the seven outputs of the 4511 and the seven pins of the display, the other five pins are connected to ground. These pins power the four digits and the dots between the numbers.
The 4511 is designed to be used with a common cathode display. The aim of this circuit is to count 0 to 9 on each of the four digits of the display. The diagram from circuit wizard demonstrates the possibility of using four switches as a means to input the 4511. An open switch represents 1 and a closed switch represents 0. Using circuit wizard as a means to experiment it allowed me to formulate a truth table. This can be used to identify the inputs needed for 4511 to display each number.
Filed under: Circuit Wizard Diagram
I used this diagram as a guide for setting up my protocircuit. When a switch is closed it connects to ground, this gives the 4511 input a low (0) when disconnected it pulls up through the resistors to give a high (1).
Filed under: clock development protocircuit
Using this truth table as guide I was able to send high (1) and low (0) binary code to 4511 BCD which then displayed the numbers on the display. I was able to do this using wire switches on the protocurcuit.
Filed under: Early Developments
Initially the aim is to just get some numbers displayed on the four digit seven segment display. I have decided to use the 4511 seven segment driver/decoder, picaxe 18x starter pack, four digit display and a protoboard. The idea is to use the picaxe 18x project board to drive the 4511 BCD and the display. The way this will work is by programming the picaxe, which will then send high(1) and low(0) code to the 4511 four inputs a,b,c and d, the 4511 then converts the binary code to seven out-put pins, which drives the numerical display.
Filed under: Data-Sheets
In order for this four digit display to work it must be compatible with the 4511 BCD chip. So it was important to identify, when purchasing the display, whether the chip works with a common anode or a common cathode display. The 4511 datasheet specified that the 4511 BCD is compatible with the common cathode display.
LED’s fall into two categories: Common Cathode, where all the 8 anode legs use only one cathode which is common and Common Anode where the common leg for all the cathode is of Anode type.
Filed under: Exchanging 4026 for 4511
After looking at the way the 4026 works it was decided to replace this with the 4511 BCD to 7-segment decoder. The problem with the 4026 was that with this circuit design, each of the digits on the display would require one 4026 ic making four in total, where as with the 4511 BCD only one would be needed for all four digits. This will simplify the pcb design. Also the 4026 resets and counts through from zero every time you change the number. This is done fast enough for the human eye not to notice, but this way still is not an efficient way of displaying the time.
The 4511 BCD decoder converts BCD into a numerical display. As with the 4026 ic the 4511 also drives a common cathode seven segment display. To illuminate one segment, the corresponding output has to be high. The 4511 has four BCD inputs, input a, input b, input c and input d. These inputs are feed high (1) and low(0) this binary code is then converted by the 4511 into numbers on the display.
