AEM 4601: Instrumentation Lab
To the right of the RCM 2000 are the connections to the controller, power supply and indicator connections. These are discussed separately below. The additional integrated circuits on the left circuit board are buffering for the RCM module. Thus any incorrect wiring will burn out one of these less expensive chips rather than the RCM itself. In addition the serial ports on the RCM 2000 are TTL level ports, which must be converted to the +/-12V levels of the RS232 standard.
- Solderless Bread Board
- Digital Inputs and Outputs
- Serial Ports
- Indicator LEDs
- Power Supply Connections
- BNC connectors
The internal connections of the solderless bread board shown above are marked with the red lines. The center portion of the bread board has a middle divider across which integrated circuits (ICs) can be inserted. The columns of jacks above and below the IC are all connected together to allow four connections to each pin of the IC to be made. The four power busses along the top and bottom edges of the bread board allow power to be distributed. Note that there is a break in the power busses at the center of the bread board that must be jumpered if you want power along the entire length of the board.
These blocks connect to Ports A, B, D and E. The labeling is as follows:
- PA0 - PA7 are bits 0 to 7 on Port A
- PD0 - PD3 are bits 0 to 3 on Port D
- PB0 - PB3 are bits 0 to 3 on Port B
- PE0 - PE7 are bits 0 to 7 on Port E
The ports on the RCM 2000 must first be configured to be inputs and outputs as required. See the setup4601.c example program for details on how to do this.
All four jacks arranged horizontally are shorted together and connect to the input or output bit labeled to the right of the connector.
This connector provides access to the Receive (RX) and Transmit (TX) lines of the Rabbit 2000 serial port B on the RCM2000 Controller and COM2 on the PC workstation. Each vertical column of jacks are shorted together. The connections labeled GND are ground, these need not be used, as the grounds on the RCM2000, the PC and the power supply are already connected internally.
The indicator light emitting diodes (LEDs) allow TTL logic level signals to be monitored. A TTL logic high level will turn on these LEDs. Note that the LEDs are buffered and the driving load presented to the signal being monitored is one LS series TTL input load. Also note that both connections for each LED are the same electrically, and are both inputs. You do not have to supply any power to operate these LEDs, they are powered internally.
These connections are to the Elenco Power Supply as labeled. The two ground connections are identical and are connected to the GND pin at the bottom that is good for connecting the anti-static wrist strap, discussed below.
The image above shows the connections between the two BNC (bayonet connector) connectors and the solderless connector. The center (positive) conductors on the BNC connectors are connected to the outside columns on the solderless connector. The shield or outside conductor on the BNC connectors are connected to the two inside columns on the solderless connector. Each lab station has two BNC cables, which are useful for connecting the scope and function generator to these connectors. There are also a BNC to banana plug cable and a BNC to banana jack converter to allow the meter to be directly wired through these connections.
NOTE: These connectors are completely isolated from all other signals. In particular the shield/ground conductors on the BNC jacks, are NOT connected to ground. If you want this connected to ground you have to add a jumper wire yourself.
OSCILLISCOPE NOTE: If you use the BNC cables to connect the oscilliscope instead of using the scope probe, you will have to change the probe setting on the appropriate scope input, otherwise the voltage readings on the scope will be incorrect. The oscilliscope probe is a 10X probe, that is, it attenuates the signal by a factor of 10 and raises the input impediance of the scope by a factor of 10 as well. The BNC cables are a 1X probe, that is, they don't affect the signal at all nor do they affect the input impediance of the scope.
Last Modified: 2011-07-01 at 10:55:06 -- this is in International Standard Date and Time Notation