NOV 28
Working on the circuit diagram of the control system, which consist of :
a) Dual Bridge driver to control the direction of current applied to the peltier module; - Components: L6120 L298
b) Temperature sensing feedback system to stabilize the color effect; - Components: TMPO4
c) Matrix control system with user interface to choose color of each grid. - Components: 5V Relay
d) Set up serial ports to communicate with computer - Components: Bluetooth(parani)/RS232(Max233)
Process:
a) Dual Direction Current Control System
The direction of current that applied to the peltier module depends on the function of heating or cooling.
To Switch the direction of current, a dual bridge driver L298 is applied.
c) Matrix control
1. One option to control the matrix circuit is to directly connect output ports to each grid. However this require a N*N order of operation for a N*N
Matrix.
For small matrix as (4*4) that we are working on now, it is still feasible.
But for larger matrix (eg 10*10 which will require 100 output), this method is obviously inefficient.
2. To use a multiplxer is another option. eg. for a 4*4 matrix, only 4 output from PIC is required.
However the drawback of this method is that only one grid could be activated at one time.
3. Two way control switches
Each grid will be activated when the corresponding COL SWITCH and ROW SWITCH are both ON
 Initially we tried to use a pair of npn BJTs to provide the 2-way switch control.
Principle: Then bulb reprenst one grid of the matrix. It only lights up when B1 and B2 are both High (in other words, both ROW and COL switches are ON)
However, after experimenting on _____ and _______, we failed to get the circuit work.
The design diagram is illustrated below:
 Afterwards, I started to experiment with 5V Relay (mechanical switches). So far it is operating as desired. I will be evaluating the drawbacks of this switch later.
The schematic of the Matrix Control Circuit and Matrix is illustrated below:
 d) Serial Communication
Working on the RS232 module
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