SLU Physics FlexLab Power Supply

Using the Flexlab Power Supply for Bewkes 231 & 232
The non-Major's Stockroom

Each stockroom contains a Flexlab unit to provide a fixed voltage through the red and black power connectors on each bench in the adjacent lab rooms. The lab bench connectors are numbered, and the corresponding numbers appear on the Flexlab unit.
Two methods are used for the distribution of voltage in our introductory physics courses:
1. Setting the voltage on the Flexlab unit for distribution to all benches in a lab (Directions). This is sufficient when precision of voltage isn't an issue (e.g. Lenz's Law)
2. Using a separate power supply in the lab, and the Flexlab unit simply distributes the voltage (Directions). This is used when a more precise voltage setting is required (e.g. The Photoelectric Effect)
  - Unless someone has been messing around with the wires, the only difference between these two configurations is the presence or absence of patch cords connected to the blue & red output connections under the voltage dial
A laminated chart of the lab bench numbers is hanging on the wall next to the Flexlab unit so that you can check that the correct benches get the desired voltage
- Bewkes 231: Connectors 1 to 10
- Bewkes 232: Connectors 11 to 20
An indicator light is located under each voltage gauge (Figure 1). They generally don't work, so you need to check the voltage dial to make sure it is turned off
Each voltage setting has a primary and secondary circuit breaker. Both must be enabled when using the Flexlab unit as the power supply
The voltage provided by the FlexLab unit tends to drift up or down after a while. Use an external power supply in the lab if you need more precise control
Note that both AC and DC voltages can be selected on the Flexlab. We only distribute DC voltages to the lab benches. It would be sheer madness to use AC voltages in this manner

Basic Operation of the FlexLab Power Unit: Up to three separate DC voltages can be supplied using the FlexLab unit. Each voltage supply section (Figure 1, within the red box) contains a voltage gauge, indicator light, two circuit breakers, voltage dial, and blue & red output connectors Two rows of connectors (upper & lower, Figures 1 and 2) allow the distribution of voltage to all the lab benches, according to the numbered connections along the bottom Each patch cable has a pin plug and a socket plug on each end (Figure 4). These are plugged into the appropriate connector in the output or distribution section (Figure 3). Note that the outermost ends of the distribution rows have connectors that accept the socket plug end (Figures 2 and 3). This makes it impossible to short out the FlexLab unit
Figure 1: An annotated view of the Flexlab unit. The large dial and white & black connectors (obscured by labels) are for AC voltages	Figure 2: Detail – patch cord connections
Figure 3: Detail of FlexLab connectors. The blue & red connectors provide DC voltage from the FlexLab unit. The black & red connectors distribute voltage to the lab benches. Note that the right-most connectors accept the socket end of the patch cord	Figure 4: Patch cord detail showing the pin plug and socket plug ends. This makes it impossible to short out the FlexLab power supply
Figure 5: Patch cords are stored nearby and available in two lengths	Figure 6: Detail – voltage gauges; indicator lights; primary & secondary breakers

Using the Flexlab Unit as the Power Supply to Distribute a Fixed Voltage: The Flexlab unit will be configured as shown in Figure 7. Make sure the circuit breakers on the FlexLab unit are open (down position) Connect the pin end of a patch cord from the blue & red connectors (any column) under the voltage dial to the outermost (socket) connectors on the upper distribution row Red = positive voltage; Blue/Black = negative voltage Patch cords should already be connected from the numbered bench connectors to the upper and lower distribution rows. Check these connections if you want Turning ON the Flexlab power supply: With the voltage dial to be used turned off, close the the primary (PRI) and secondary (SEC) breakers above the voltage dial by flipping up Turn the voltage dial clockwise slowly until you reach the desired voltage Use a voltmeter to check some of the lab bench connections Turning OFF the Flexlab power supply: Turn the voltage dial fully counter-clockwise slowly until the voltage is zero Open the primary (PRI) and secondary (SEC) breakers by flipping down	Figure 7: Configured with Flexlab unit providing voltage to Bewkes 231

Using the Flexlab Unit to Distribute a Fixed Voltage from an External Power Supply in Lab: The Flexlab unit will be configured as shown in Figure 8. Make sure the circuit breakers on the FlexLab unit are open (down position), and that any patch cords connected to the blue & red connectors are removed Connect a DC power supply to one of the lab bench connectors (I use #5 in Bewkes 231) Patch cords should already be connected from the numbered bench connectors to the upper and lower distribution rows. Check these connections if you want Do not connect patch cords from the upper distribution rows to the blue & red connectors under the DC voltage dial Make sure the patch cords from the connectors where the external power supply is attached (e.g. #5) is connected to one of the distribution rows Turn on the external power supply and use a voltmeter to check some of the other lab bench connectors	Figure 8: Configured to use a separate power supply in the lab

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©Jeffrey R. Miller	St. Lawrence University	Department of Physics