Power up!
Ensuring Proper Power Connections

Setting up a new behavioral test system, including the computer, interface equipment, and control cards, can be a daunting task. The unmatched flexibility and power available to the user through our MED PC®-controlled test systems does bring with it some challenges, such as routing cables, plugging in response devices and stimulus devices correctly, and ensuring that everything is addressed properly.

Sherie Kojtari, B. S., lab technician at Catamount R&D/Med Associates, gets started in the lab by setting up her first Med-PC® Interface system. It doesn't have to be a tangled mess of frustration. With a little careful planning, and understanding how everything should connect, you too can have organized and proper cable configurations in your Med-PC® Interface.

One common question we get relates to powering up a new system. Some times everything seems to be wired correctly, but you go to start your first experiment and lights don’t turn on when they are supposed to, or lever presses don’t get counted. The place to start looking for the answer to this problem is the power supply.

The interface modules that control stimulus and response devices are installed in a rack mount chassis, which many people call “the blue box,” or “the interface cabinet.”

Currently, most of our interface cabinets have power supplies that are built into them. In addition, they usually have a modular card called a “Decode” card installed in the left-most slot.

This card connects the computer to your interface cabinet, routing the instructions from the computer to the interface cards in your system, and taking data from the interface card back to the computer. Furthermore, the Decode card is necessary for getting power to all of your experimental chambers. This card has four indicator lights (LEDs) that illuminate when the power supply voltages are operational. In a system that is functioning normally, all four LEDs on the Decode card should be on, indicating 5 V, +15 V, -15 V, and 28 V are all operational. If any of these LEDs are not lit, you will most likely be having problems with the functionality of your system.

The most common problem people experience, particularly when setting up a new system, is that the 28V power LED on the decode card is not illuminated, and none of their lights/levers work. If you are using our 28V SmartCtrl™ interface or standard 28V input/output interface modules, the 28V power LED on the decode card should be on for proper functionality.

Problem: 28V light on Decode Card is off, no inputs or outputs work.

First, make sure the 28V cable connection is correct. Proper connection of the 28V cable is probably the most common source of confusion.

• The Decode card has a 2-pin power connector located near the bottom of the panel. This connection is for 28V power INPUT. This connection often gets mistaken for an output. Make sure to connect a cable from the 28V power supply to this 28V connector on the Decode card. The Decode card will then properly route 28V power to the I/O cards located in your interface cabinet.

Some common configurations for power supplies and interface cabinets are discussed below.

Larger interface cabinets (e.g. SG-6510D) usually have a 28V power supply that routes 28V outputs to a module on the front of the chassis (see Figure 1). One of the 28V outputs on this module should be connected to the 28V input connector on the Decode card, as shown in Figure 1.

Some smaller interface cabinets (e.g. SG-6080D) have the 28V power outputs routed to the back of the interface cabinet (Figure 2). The four 28V connectors on the back of this style interface cabinet all supply 28V outputs. To properly connect the decode card, simply run a 28V cable from any one of these rear output connections around to the front and plug into the decode card connector (Figure 2). On new units there is usually a short cable plugged in back here that is just long enough to reach to the front and meant for this purpose.

In some cases, particularly with large multi-box systems, all of the slots in the interface cabinet are used for I/O modules, and there is no 28V power supply internal to the interface cabinet. In this case, an external 28V power supply (e.g. SG-500 series) is needed (Figure 3). Simply run a 28V power cable from any one of these outputs to the connector on the front of the Decode card. Don’t forget to turn this supply on with the rest of the system. It has it’s own power switch.

Making it All Connect

In most cases, especially when using SmartCtrl™ I/O modules, you will need to get 28V power to your experimental chambers to control lights/levers/pellet feeders/etc. The SmartCtrl™ I/O modules connect to your chamber via an SG-716 series “Breakout Box”, or “Connection Panel.” On SG-716 series Connection Panels, there are three 28V connectors located at the bottom of the Connection Panel, as shown below (Figure 4). You need to connect a 28V power cable from your 28V power supply to any one of these connectors. All of the 28V power connectors on the Connection Panel are tied together internally, so you can plug into any one you want to supply power to the box. Since they are all tied together, you can use the other open connectors on the Connection Panel to daisy chain power to other boxes or fans.

Daisy chaining allows you to simplify some cable groups. This is the process where you have a 28V power supply output module and run a cable from this point down to your first Connection Panel as described above. You can then run another 28V power cable directly from the first Connection Panel to a second Connection Panel, and another cable from your second box to a third, and a third to a fourth. The limit is four boxes total on any one power chain group. Remember though, you always need one Connection Panel tied back to the actual 28V power supply.

Why or where would you daisy chain 28V from one box to another?

One interface chassis with MED-PC® software can run up to 16 animal chambers. If you had an SG-716 Connection Panel on each of these 16 chambers, for example, you need power for each Connection Panel. If you ran a separate power cable from the supply to each Connection Panel, you would need 16 output connectors on the power supply. Power supplies usually do not have that many power outlets available on the power supply. Daisy chaining would allow up to 16 chambers to run on four power supply output connectors (one power output connector to four daisy chained boxes, times four power output connectors equals 16 chambers total.

Using the 28V Connections on the Connection Panel to Power a Fan

The 28V connectors on the Connection Panel can also be useful to run fans. Once 28V power is connected to the Connection Panel, the other 28V connectors on that Connection Panel now also carry the power voltage. If you plug a fan into an open 28V connector, you would end up with a fan that runs any time power is applied to the system (for simple ventilation). If you need to control the fan flow during testing, you would need to connect the fan directly to a standard 3-pin Molex Output connector on the Connection Panel that you control as an Output from MED PC® software (Figure 4). Connecting the fan to a 3-pin Molex Output connector requires a separate adapter cable (part number SG-216B4), which is included in most systems.