uboone - fermilabhuffman/microboone/fusedcable... · 2015-03-12 · 3/12/2015 1 david huffman -...

3/12/2015 David Huffman - uBooNe FusedCableDescription.pptx1

uBooNeMPOD Fused Cable Connector

• The Wiener power supplies used to power the flange electronics presents some issues that need to be addressed in order to use them at Fermilab.

• A safety concern arises because the output of the supply uses multiple pins for each voltage. These pins are rated for 5 Amperes and 3 pins are used to supply the possible 10 amperes the output could produce.

• Fermilab has guidelines that requires derating current capacity when multiple pins are used in parallel. The rule of thumb is 2/3 the rated capacity. So for a 5 Amp rated pin we can run 2/3*5= 3.33 Amps.

• This value agrees with the manufactures de-rating curve seen on the following page if temperatures are kept below 50°C.

• We will arbitrarily pick 50°C for the maximum temperature and 3Amps for the maximum current for the D-Sub connector.

37 Pin D-Sub De-Rating Curve


MPOD Output(Top Connector Shown)


Sensing

Sensing

Sensing

Sensing

Output Connector

• Since we can only operate 3 Amps on a single pin, that pin will have to be protected. Construction of a special connector will accommodate our needs.

• Each current carrying pin can be fused at 3 Amps. The 3 pins will be tied together, in parallel, going to one wire (18AWG) large enough to carry the full 10 Amps the supply can deliver.

• The final protection is fusing, the main protection will be the supply settings, Over Current and Current Limit. We will set them above the operating current but below the fuse value.


Output Connector

• A printed circuit board will be used to accomplish this and all components will fit inside a commercial connector hood with two cable exits.

• For the fuse to work it will have a voltage drop across it that produces heat. This is the main heat producer and needs to be kept below the maximum.

• The heat will be spread and conducted to the metal shell (hood) with thermal foam.


MicroBooneCable Build Assembly


Sensing leads are connected to the power leads on the fuse card at the load end of the cable.

Four 18AWG power leadsFour 22 AWG sensing leadsUp to 10meters long

37-pin D-Sub

Molex 39-01-40505-pin

U0 & U1

U2 & U3

Cable Lengths

• We need the following cables assembled.

• Quantity Length• 1 14 ft.• 2 16 ft.• 4 20 ft.• 2 24 ft.• 2 27 ft.• 2 29 ft.• 2 31 ft.• Total = 15 Cable Assemblies


MPOD Fused ConnectorUnder the Hood


File enough here (both sides) so the PCB does not touch hood. Remove material to the bottom of the P33 lettering.



PCB Top Right and Left

Drain wire connects to shell.

2” black shrink-tubing



PCB Bottom -3.3V Right and Left

Thermal Pad

• We will use a thermal pad to spread the heat across the connector hood. Apply to both shell halves.– Bergquist BER225-ND 80mil


Fused PCB


Multi-conductorCable

• Custom fabricated multi-conductor cable, Plenum rated.• 2 x 18 AWG twisted pair (Red/Black) (White/Green)• 2 x 22 AWG twisted pair (Orange/Yellow) (Brown/Blue)• Foil shield with drain wire• Pair Red/Orange; Black/Yellow; White/Brown; Green/Blue


Line Drawing


Molex Details


Note very hard to see labels

Easier to find 1, 2, 3 Ribs

Molex End

• The load end of the cable will have a fused card that terminates into a 5-pin Molex connector 39-01-4050.

• The following chart gives the de-rating current at 7 to 8 Amps for four conductors.

• Limiting the source from 6 to 7.5 Amps will be the design goal. Therefore three 2 or 2.5 Amp fuses will be used at the source end for 6A to 7.5A.

• Sensing wires will be fused for 2A near the connector.


Sensing PBC Cover

• Sensing board cover


BOM

• 37 Pin Sub-D Fused Board– 1 PCB FNAL # 176882A– 1 37 pin Sub-D – 12 2A Fuse #0157002.DR– 1 Dual outlet Hood #1534811-1– 2 Rubber Grommet #747746-1– 2 80mil Thermal Foam Bergquist #BER225-ND

• Custom Cable & Hookup Wire– Two 18 AWG twisted pair & two 22 AWG twisted pair.– 18 AWG hookup wire; Red, Black, White and Green.

• Sensing card– 1 Fused Sensing card FNAL # 176904– 2 2A fuse #0157002.DR

• Molex Connector– 1 Five pin Molex connector #39014051– 5 Female pins #39000428

• Plastic Cover– 2 Grommets #747746-1


Molex 39-30-3057Current Rating Chart


Testing

• Testing was conducted with all pins connected in series so each pin had the same current flowing through it. Each group of three pins are parallel however some difference in current is seen because the resistance of each fuse is slightly different.

• Testing was repeated with different fuse values for comparison. This should provide enough data to decide proper operation.

• What is needed is the maximum current fuse that can be used to keep the temperature at a minimum, yet a small enough current to protect the pins.

• With the target operating value of <5 Amps three 2 Amp fuses in parallel should be adequate.

Fuse choice will be Littel 3A NANO 157 series Time Lag #0157003.DR (This size fuse will source more current than the circuit inductor can handle.)Littel 2A NANO 157 series Time Lag #0157002.DR (Use this value!)


Measured Temperature Curve


uboone - fermilabhuffman/microboone/fusedcable... · 2015-03-12 · 3/12/2015 1 david huffman -...

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