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.
I intend to use this project board and the 18x picaxe to drive my four digit seven segment display. Using all eight outputs, I intend to use four of them to drive the 4511 BCD and the other four power the four individual digits. The benefit of using the PICAXE system is that programs are downloaded via a direct cable link straight into the microcontroller. I will program the picaxe with the use of programming editor, which can be downloaded from the picaxe web-site. Using the program language basic I intend to create a programme that will allow the time to be displayed.
Filed under: Final Design
This video shows how I want the clock case to look. When the clock is turned around you can see where I plan to put the electronics.
Filed under: Mass Production
Clock Casing
The casing for my clock if put into mass production would be injection molded. This involves forming the mold which could be done by electrical discharge machining (EDM). This process allows prehardened molds to be shaped so that no heat treatment is required. The process uses a shaped electrode normally made from graphite or copper. This is lowered into the mold surface which is immersed in paraffin oil. A voltage is added which sends electrodes between the mould and the tool which causes erosion of the mold surface in the inverse shape of the electrode. Once the molds are formed these are closed and heated plastic can then be forced into them using the pressure of the injection screw. The plastic then takes the shape of the mold.
A lot of consideration and thought needs to be put into the design of the molded parts of the clock. This ensures that the parts will not be trapped in the mold and that the molds can be completely filled before the molten resin solidifies. This compensates for material shrinkage and minimises imperfections in the parts.
For this design the casing would be made in two parts, these two parts are called the core and the cavity. To ensure the mold does not get stuck, the direction from which the core and cavity are removed from each other need to be angled. Due to the bucket like shape of the casing, after the molding process the casing is likley to shrink in its mold. Pins would be the popular method of withdrawing the mold from the core. Other methods for withdrawing the mold are but air ejections, and stripper plates.
A mold can produce several copies of the clock cassing part at the same time, the number of coppies is known as cavitation. For the production of this clock casing a multi -cavity tool would be used.
Filed under: Final Design
This is my final design drawn in pro desktop. The idea is to go for a design that is minimalist in its looks but as sleek as possible in its design. As I am aware of the amount of time I will spends on the electronics and programming for the clock, the aim for the casing was to have a simple design that is as appealing as possible.
