Fixed card attachment[/edit]
So I have been working on this for a while now, and being an INTJ I tend to (over)think things through before finally jumping in. Last week I purchased a bunch (to me) of electronics including switches, logic gate ICs, diodes, shift registers, etc. For power, I purchased a 100a 5v power supply.
Anyway, after drawing a few circuits out I came up with an interesting solution. The project is a 10x10 miniature split-flap display, so 100 individual displays. Most of these projects are done with stepper motors but this is costly. I am trying to keep this project within a $1500 limit and 100 steppers+controllers would put me right there without anything else. Instead, I have been trying to get around this by using inexpensive dc motors + physical switches and ICs.
The program starts by shifting out the bits needed to only get a HIGH signal on the S5 switch (the one corresponding to the BLANK card). The OR gates send HIGH because the S5 is still closed, the mosfet activates allowing current to flow to the motor. Once the BLANK card is rotated into the switch bank, it activates the switch, opening the circuit. This means the OR gates send LOW signal out which deactivates the mosfet which kills the motor.
After that, bits will be shifted out for specific displays. IF the next display to be sent is lower than the previous display (a 3 when a 5 was displayed) the signal to the BLANK will be sent first and then the correct display (5 → BLANK → 3). For the other displays, a LOW signal will be shifted out to those so the motor does not run (2 → 6 → null). For the displays that remain the same a LOW signal will be shifted out to those each time (4 → null → null).
The possible issues.
- This will require 60 shift registers to work. I have initially purchased 25 to see if I can send reliable signals that far (I should have just bought 60 knowing I would need them and would have to test the signal regardless). Will I need some sort of signal amplifier to make sure the signals don’t get degraded?
- I have purchased diodes but don’t know exactly where to place them. Just inline after the mosfet, before the motor’s negative lead? Or in parallel to the motor between the positive and negative leads?
- I purchased 10k and 100k resistors for pulldown purposes.
a) Do I just need one off the pin from the arduino
b) Do I need one for each register
c) Do I need them for the OR gate IC inputs (can’t imagine that I do since the switches are physically open/closed if I want the IC’s to operate)?
Note in the diagram, the series of OR gates is accomplished through two 3-input OR gate ICs in serial, but the app I used (schemeit from digikey) is limited to 2 input gates.
So how much did I screw this up? Did I miraculously get this close to correct?