It uses a single ULN2803 or ULN2003 to select a group of 4 bus signals out of 16, namely D0 to D15. If you use a ULN2003, you simply make sure it plugs into the correct spot on the socket. This is bottom justified leaving pins 1 and 18 of the socket blank.
Boards are cascadable so that 16 relays could be run with 4 boards.
The relay base layout is the same as my old relay board. This allows a wide range of relays to be used. If I was to design it for just one type, it could have been a lot smaller. It's length is 2.65", so I have called it a 2.5 Inch platform.
The AUX VBB/GND input terminals may appear to be in an awkward spot but my friend Mick convinced me that this isn't a problem. If it goes in a SIMM socket, you connect up the power before inserting it. If it connects via male/female pins, it isn't a problem anyway.
Has 4 LED's and resistors across the coils so that visual operation can be seen. 560 Ohm resistors have been chosen so that 5 to 12 Volts can be readily used on the LED's and coils.
For testing, a 3 pin header is provided so that VBB can be easily jumpered to either
+5V or PWR signals on the SimmStick Bus.
1 by DT205 PCB
NOTE *** If your DT205 is only going to be set for a group of 4 signals then you can solder your chip straight into the board, or at least use a single socket.
If it is for development, it would pay you to get the 8 strips of socket pins so that any group of 4 signals can be selected.
If using D0 to D3 to drive the four Relays, install your ULN2803 into the E1 pin 1 position. This is shown on the overlay as '1' and lines up with '8'. The 8 signifies that you are using an 8 bit driver chip. If you were to use a 7 bit ULN2003 driver I.C., then pin 1 lines up with '1' and '7'. This will leave pins 1 and 18 blank on the socket.
The only difference between the two chips is the extra gate and two extra pins at one end of the chip, so either chip can be used as only 4 gates are connected to the Relays. Just make sure that you bottom justify the chip to line up with the ground and VBB pins.
For D4 to D7 install your chip into E2, same principles as before.
All hand assembly should be done by installing the shortest height components first.
I would suggest:
Then insert your chip. You are finished.
The walking LED test program sample is all you need to make this board work.
The 560 Ohm resistor has been chosen so that it can be used with both +5V and approx. 12 to 15 Volts. Power can be supplied to the board from one of 3 sources.
The DT205 Relay board can be plugged straight into a SimmStick bus via a SIMM Socket, or it could be mated with a main-board or motherboard using right angle male and female pins. If the later is done, you can then solder a right angle female connector to the board so that additional Relay boards can be added.
NOTE **** Only the SimmStick bus signals D4 to D15, plus
PWR, +5V, and ground are allowed to continue on the bus, so if you are using D0 to D3 for
Relays, then this board must be the first in the chain.
The relay coil can be at .1, .2, .3, or .475" centers. The row of holes below the relay coil are at the .1" pattern. The lower large hole is used for the common connection relay contact on some relay types.
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