|
|
HowTo: 128 chan derivative of Hill's 320 design w/ PCB and Linux driver
( Don Law)
Step 4 : A subcontroller
|
| | Each subcontroller handles 6 channels. It takes 6 triac drivers,
6 triacs, 12 resistors, and 3 double sockets plus wire. The triac drivers
are MOC3023 chips that I got from Jameco for about 30 cents each.
The MOC3023 only takes 5 mA to trigger, so I chose to drive it
straight from the 74LS374. I don't know exactly what the max
current output of a 74LS374 is, but at least mine aren't getting
warm. :-)
The triac drivers are the white chips on the left side of the
photo. I used the
resistive load schematic
right from the Fairchild documentation for the part.
It amounts to a 470 ohm resistor between the output of the
74LS374 on the master controller and pin 1 of the MOC3023.
Pin 2 goes to ground.
On the triac side, there is a 180 ohm resistor between pin 6 and
the load side of the triac.
For the triacs, I used a nice 8 amp isolated triac from Sanrex, part
number TMG8C60F. I made my own heat sinks out of old license
plates. I just cut one square and drilled 6 holes for the mounting
screws. I got the triacs for about 76 cents from Jameco.
I got the sockets for less than $4 for a pack of 10 at home depot.
The resistors are 1 cent in 100 qty. That brings the cost of
a subcontroller to about $7.50 plus wire.
|
|
|
