Electronics Setup and Cabling

1. Mounting and Powering up the Electronics Backpack (a.k.a., the E-Box)
   1. Mounting and Cabling:
   2. Powering up:
2. Mounting up the Lockins, DAS, and Associated Electronics
3. Cabling!
   1. Signal cabling in the e-box
   2. from the e-box to rest of world
   3. from lockins to DAS
   4. auxiliary cabling
   5. power cabling at DAS rack
   6. AC power and grounding
4. Configuration of the Bias Board(s) for Various Modes
   1. Rev 2 Bias Board
   2. Rev 3 Bias Board
5. Cabling for DC Bias Skydip IV Curves
6. Revision History

Mounting and Powering up the Electronics Backpack (a.k.a., the E-Box)

Mounting and Cabling:

1. With the e-box on the ground, move all the Cable G's (the 55-pin-circular-to-DB50-and-DB9 cables) out of the way of the horseshoe-shaped slot on the bottom of the front part of the box.
   
   
2. Get a set of screws ready for mounting the e-box to the dewar.  These should be found in the electronics box section of the dewar screw container.  They are just 8-32 socket heads.  Get a 9/64" ball driver ready.
   
   
3. Lift up the e-box and align the horseshoe slot with the circular hermetic feedthroughs.  This can be done by one person but is much easier with two.  Make sure you don't catch anything under the e-box.
   
   
4. Line up the screws and get a couple of the front-most (furthest from the rest of the box) screws in to carry the weight.  Don't tighten them.
   
   
5. Get more screws in their threads.  You only need to put in every other screw.  Don't tighten until all the screws are in.  Then tighten them all down.
   
   
6. Mate the circular connectors to the hermetic feedthroughs.  You have to be very careful to avoid damaging the hermetics:
   
   
• Start with hextants 3 and 4 and work away from the midline.
  
  
• Find the keys and slots and make sure you start out with them all aligned.
  
  
• Push the connector down onto the feedthrough and make sure you feel the pins aligning with the sockets.
  
  
• Gently rotate the locking ring a little bit, push a little bit, rotate a little bit until the connector is all the way down and you can hear the locking ring catch.  The idea is to not use the locking ring to apply force because it is hard to tell if you are causing damage or not.  Push from above to get the connector to move down, then the locking ring will be a little slack and can be tightened up.  Repeat until done.
  
  
• Note that the fridge feedthrough's keys (the leftmost connector) are not aligned the same way as the rest of them.
  
  
7. Check that the bias board spider cable (DB50 to 6xDB9) is well mated to the DB9s on the Cable G's.  Make sure all the jackscrews are tight -- those bias connections are very important!
   
   
8. Connect up the power cable to a PSU as indicated on the Fridge page.

Powering up:

1. Each switch near the DB50s on the Cable G side of the backpack corresponds to one slot in the rack and has a LED to indicate it is on.  Note that the bias board is double-wide and so one switch is not used.
   
   
2. Each preamp should draw about 300 mA from both the + and - supplies.
   
   
3. The bias board draws about 250 mA from each supply when not connected to the JFETs, about 300 mA when connected.
   
   
4. The thermometry boards draw a total of about 50-60 mA together, more for the fridge board.
   
   
5. Beware of any readings taken without both the bias board and the preamps on.  The preamps can load the JFETs if they are not turned on, which results in funny current flows from the bias board.
   
   
6. Make sure all front panel switches on the fridge and auxiliary thermometry boards are in the HIGH R state; if they are in the LOW R state, the fridge monitor readout will be wrong and the boards may overheat the fridge.
   

Mounting up the Lockins, DAS, and Associated Electronics

Cabling!

Signal cabling in the e-box

• Cable G's all connected to dewar, thermometry cables also
  
  
• thermometry cables connected from outputs of thermometry boards via RF feedthroughs on bottom of e-box:
  
  
• fridge board: short DB50F-DB50M cable connects from bottom output of board to feedthrough
  
  
• AUX board: long DB50F-DB50M cable connects from top output of board to feedthrough if using array and IC diodes, otherwise uses bottom connector.
  
  
• GRT (germanium resistance thermometer = focal plane thermometer):
  
  
• During testing, the GRT cable connects from the bridge to the top output of AUX board, the shell must be explicitly grounded to the e-box using clip lead.  The GRT cable is a DB15F-DB50F cable made of two white twisted-pair cables held together by heat shrink joined to a 40-foot extension cable that consists of two grey twisted-pair cables held together by cable ties and is DB15F-DB15M.
  
  
• During observations, we pull the AUX board and use a special "inside-the-e-box" GRT cable to go from the backplane feedthrough to the output feedthrough on the bottom of the e-box.  This cable is DB50M-DB50M and consists of two white twisted-pair cables heat shrunk together.  This connects to the LR750 resistance bridge via the aforementioned DB15F-DB50F cable (including the extension).
  
  
• bias board output connects via long DB50F-DB50M cable to output feedthrough
  
  
• preamp outputs connect via either long (DC mode) or short (AC mode) DB50F-DB50M cables to the output feedthroughs

from the e-box to rest of world

• power cable connects to PSU.  See the section on AC power and grounding for details.
  
  
• thermometry cables connect to fridge rack white breakout box as described on the Fridge page, except the AUX cable is not used and the GRT cable is used instead when observing
  
  
• in instrument testing mode (i.e., IV curves with temperature control), the bridge chassis may need to be grounded to directly to the e-box by connecting an alligator-clip lead from the chassis screw on the back of the bridge to the e-box.
  
  
• bias and preamps:
  
  
• DC mode: long preamp-to-lockin cables (DB50F/DB50F) or topologically identical test cables for preamp signals, an additional topologically identical cable for bias, all go straight to DAS input adapters
  
  
• AC mode: bias spider + long preamp-to-lockin cables to lockins
  
  
• bias spider DB50F connects to input of bias monitor lockin box
  
  
• bias spider 4xDB9F connects to LOCKIN REF inputs of the 4 lockin boxes

from lockins to DAS

• bolometer lockin AC output signals connect via DB50F/DB50F cables to DAS multiplexer module inputs for modules 1, 3, 5, 7, 9, 11 (hextants 1(A), 2(F), 3(E), 4(D), 5(C), 6(B)) via DB50/DB25-to-DIN96 adapter boxes
  
  
• bolometer lockin DC output signals connect via same arrangement to DAS multiplexer modules 2, 4, 6, 8, 10, 12 in same hextant order
  
  
• bias lockin AC output signals connect via special DB50F/DB25F cable to DAS multiplexer module 11 via the DB25 connector of its DB50/DB25-to-DIN96 adapter
  
  
• bias lockin DC output signals connect via same arrangement to DAS multiplexer module 12
  

auxiliary cabling

• Use the following diagram:
  
  
  
  
  
• Picture of the DIGITAL I/O BOX
  
• Picture of the CSO-DAS OPTOISOLATOR BOARD
• Picture of the CSO TTL I/O (blue and silver boxes)
• Picture of the ROTATOR LIMIT SWITCH
• Picture of the LR750 Resistance Bridge
• Picture of the Chopper Rack, in particular the chopper controller. 
  
  
• Logic signals from the telescope and allegro (ACQUIRED, TRACKING, OBSERVATION NUMBER, READY-TO-ROTATE, ROTATING) are received by row 1 BNCs on the CSO-DAS OPTOISOLATOR BOARD that sits above the DAS computer in the DAS rack.  If you feel like it, you can connect the ROTATOR LIMIT SWITCH, though it's not really necessary.  The CSO-DAS OPTOISOLATOR BOARD converts them to signals referenced to DAS rack ground and sends them out via a DB50F/DB25F to DAS multiplexer module 1 via the DB25 connector of its DB50/DB25-to-DIN96 adapter (similar to bias monitor lockin signals).  The BNCs on the CSO-DAS OPTOISOLATOR BOARD are labeled by signal assignment and their ordering is indicated in the diagram.
  
  
• Analog signals from the GRT resistance bridge and the chopper encoder are received by the row 2 BNCs on the CSO-DAS OPTOISOLATOR BOARD as indicated above.  These BNCs are not optoisolated; the board sends them straight through to a DB50M connector, which is then connected to DAS multiplexer module 2 via the same arrangement as for the opto-isolated signals.  Once connected, make sure you are getting reasonable readings for these signals: they are absolutely crucial to our analysis!  Specifics for each channel:
  
  
• GRT: Connect the ∆R analog output on the back of the bridge to the leftmost BNC in row 2 of the CSO-DAS OPTOISOLATOR BOARD.  (The BNC is labeled as such).  Bridge settings:
  
  Resistance range: 200 kΩ
  Excitation voltage: 2 mV
  RSET = 0 (press the RSET button and enter 0 using the keypad)
  ∆R x 10 button is off
  
  The analog voltage you should see at the DAS on channel 56 is -(RGRT/200kΩ) x 10V
  
  
• CHOP_ENC: There should be a cable coming up from the sidecab that is labeled CHOP_ENC or some such thing.  It carries an analog signal that is proportional to the chopper position.  Connect it to the 2nd BNC from the left in row 2 of the CSO-DAS OPTOISOLATOR BOARD.  To check, the simplest thing to do is turn on the secondary chopper using the command
  
  
  UIP> SECONDARY 90 1
  
  
  which results in the secondary swinging 90 arcsec (+ beam to - beam) at 1 Hz.  The encoder calibration is: voltage offset is 0.388 V, scale is 88.1 arcsec/volt.  So, on channel 57 of the DAS, you should see a rolled-off square wave oscillating between -0.123 V and 0.899 V.  Turn off the chopper using
  
  
  UIP> SECONDARY /STOP
  

power cabling at DAS rack

• The Topward 6036D-10 power supply sits in the DAS computer rack.  A short triple-banana-to-DB15F cable connects this PSU to a power breakout board in the lockin rack (the cable is of the same type as used for the e-box power supply, see the Fridge page).
  
  
• The power breakout board converts from the single DB15 from the PSU to 5 DB9 connectors; these provide power to the 4 lockin boxes in the lockin rack and to the CSO-DAS OPTOISOLATOR BOARD in the DAS computer rack.
  
  
• The ground line is connected to the DAS rack by a grounding lug.
  
  
• Both racks are strapped together.
  

AC power and grounding

• The Topward 6306D-10 power supply on the lockin/DAS rack can be used to power both the e-box and the lockin/DAS racks: it has a current rating of 6A, which should be enough for everything.  So, connect both the e-box power cable and the lockin rack power cable to this supply (both are triple-banana-to-DB15 cables, the e-box one is much longer, of course).  This PSU should have its ground line strapped to the rack it sits in, and the two lockin/DAS racks should be strapped together.  Its AC power cable should be plugged into clean power.
  
  
• The resistance bridge's AC power cable should be plugged into clean power.  Its chassis is grounded to the lockin rack because it is mounted in the lockin rack.
  
  
• The temperature controller, when in use, should have its chassis tied to the resistance bridge (or directly to the lockin rack) and it should also use clean AC power.
  
  
• The DAS multiplexer chassis and the DAS computer chassis are automatically strapped to the DAS rack by their mounting frames.  They should be powered from dirty power.
  
  The multiplexer modules have differential instrumentation amplifier inputs that convert between the differential input signal and their ground reference, and the ADC board in the DAS computer is similar.  So it's ok to power them off dirty power because the differential readout removes any common mode voltage between clean and dirty power grounds, and the common mode voltage is also minimized by having all the chassis strapped together.  The reason for powering them off dirty power is that the multiplexer, ADC board, and computer all have fast clocks that can cause high-frequency glitching on the power supply lines because of the fast current draws.  We don't want these glitches to make their way into the sensitive analog electronics, so we power these dirtier parts of the system off dirty power.
  
  
• The fridge heater power supplies sit in a different rack.  No connection need be made between that rack and the lockin/DAS racks since the fridge signals are relatively coarse, high-level, differential signals.  The fridge heater supplies should be powered from clean power because we don't want glitches on the dirty power lines to be communicated into the dewar via the fridge heater lines. 
  
  One might worry that glitching from dirty power might feed back into the dewar via the signal lines going from the fridge and AUX boards into the white fridge breakout box and from there into the DAS computer fridge ADC board.  This is unlikely since the ADC board is not actively driving its input lines; the ADC inputs are differential and high impedance, so they are unlikely to be feeding anything back to the dewar.  If one is worried, one could disconnect the connector that goes between the white fridge breakout box and the DAS computer.  Note that one must leave the white fridge breakout box connected to the dewar and the fridge power supplies in order to run the fridge and power the IC 3He heat switch heater during observing.

Configuration of the Bias Board(s) for Various Modes

Rev 2 Bias Board

• AC/DC switch in DC mode
• INT/EXT switch in INT mode
• If you don't want cross-talk from the bias oscillator clock, flip the CLOCK INT/EXT switch to EXT and put a shorting cap on the adjacent BNC.
• Adjust the bias using bottom-most potentiometer, labeled DC.
• If you want 0V bias without turning the bias knob, flip the AC/DC switch to AC mode and set the CLOCK INT/EXT switch to EXT mode.

• AC/DC switch in DC mode
• INT/EXT switch in EXT mode
• Flip the CLOCK INT/EXT switch to EXT and put a shorting cap on the adjacent BNC.
  
• run a BNC from the triangle wave output BNC to EXT input BNC (the other two BNCs on the front of the board in addition to the CLOCK BNC).
• TRIANGLE WAVE ENABLE switch enabled (in lower right next to DC bias knob)
  
• To set the amplitude, vary the DC bias adjustment knob (don't go into the board and set pots).
• You can ground the triangle wave to get offsets by setting the AC/DC switch to AC mode.
  

• AC/DC switch in AC mode
• INT/EXT switch in INT mode
• CLOCK INT/EXT switch in INT mode
• Adjust the bias using 2nd from bottom potentiometer, labeled AC.
• To get 0V AC bias without turning the bias knob, flip the AC/DC switch to DC.  This will actually apply a DC bias.  You can also flip the CLOCK INT/EXT switch to EXT and put a shorting cap on the adjacent BNC, or go to DC mode and set the DC pot to 0.

• AC/DC switch in AC mode
• INT/EXT switch in EXT mode
• CLOCK INT/EXT switch in INT mode
• Run a BNC as for triangle-wave DC mode.
• TRIANGLE WAVE ENABLE switch enabled (in lower right next to DC bias knob)
• To set amplitude, vary the AC bias adjustment knob (don't go into the board and set pots).
• You can ground the triangle wave to get offsets by flipping AC/DC switch to DC or flipping CLOCK INT/EXT to EXT with a shorting cap on the adjacent BNC.
  

Rev 3 Bias Board

• AC/DC switch in DC mode
• INT/EXT switch in EXT mode
• Rotary switch to "0-5V"
  
• If you don't want cross-talk from the bias oscillator clock, flip the BIAS CLOCK INT/EXT switch to EXT and put a shorting cap on the adjacent BNC.
• Adjust bias using the potentiometer knob labeled "0-5V".
  
• If you want 0V bias, turn the rotary switch to "0V".
  

• AC/DC switch in DC mode
• INT/EXT switch in EXT mode
• Rotary switch to triangle wave mode (the picture that looks like a triangle wave)
  
• Flip the BIAS CLOCK INT/EXT switch to EXT and put a shorting cap on the adjacent BNC.
• You cannot vary the amplitude of the triangle wave from the front panel.  To vary the amplitude, you need to pull the board out and turn one of the trimpots.
  
  • The trimpots to adjust are R3 and R4, trimpots near U4, a OP400 or OP470.  R4 controls the overall amplitude of the triangle wave.  R3 controls the offset. 
    
  • In general, you will want to tune R4 to get the desired current range and R3 so that the triangle wave runs from 0V to some maximum voltage. 
    
  • If you don't know where these components on the board, you can  look up the schematic on the Bolocam Electronics and Wiring internal page or in the black Bolocam binder.  
  • You should only need to do adjust the triangle wave if the optical loading has changed substantially.
• You can ground the triangle wave to get offsets by turning the rotary switch to "0V".
  

• AC/DC switch in AC mode
• INT/EXT switch in EXT mode
• CLOCK INT/EXT switch in INT mode
• Rotary switch to "0-5V".
• Adjust bias using the potentiometer knob labeled "0-5V".
• If you want 0V bias, turn the rotary switch to "0V".
  

• AC/DC switch in AC mode
• INT/EXT switch in EXT mode
• CLOCK INT/EXT switch in INT mode
• Rotary switch to triangle wave mode (the picture that looks like a triangle wave).
• Again, you cannot vary the amplitude from the front panel.  To vary the amplitude, you need to pull the board out and turn one of the trimpots.  See the schematic on the Bolocam internal Electronics and Wiring page.  You should only need to do this if the optical loading has changed substantially
• You can ground the triangle wave to get offsets by turning the rotary switch to "0V".

Cabling for DC Bias Skydip IV Curves

1. Replace short cables inside E-box (from preamp outputs to RF feedthroughs) with long cables, connecting the long cables to the DC (top) outputs of the preamps; the short cables were connected to the AC (bottom) outputs.  You should find these longer cables in the 3rd floor Bolocam storage room.
   
   
2. Disconnect the lockin-to-DAS cables for the DC LOCKIN signals at the DAS end, leave them hanging there to maintain their order.  These are the cables going into modules 2, 4, 6, 8, 10, and 12 (where the left-most module is module 1).
   
   
3. Disconnect the monster preamp-to-lockin cables at the lockin input end and connect these directly to the DAS inputs that you just disconnected.  The cables should be attached in the following order:
   
   MUX  2: HEXTANT A 1
        4: HEXTANT F 2
        6          E 3
        8          D 4
       10          C 5
       12          B 6
   
   
4. Set up kludge cabling for readout of bias monitor signals:
   
   
• Run a long DB50/DB50 test cable from the preamps to the lockins.  You will probably need to string together two cables, one M/F, the other F/F.  You don't need to tie this cable down very well, it will be removed afterward.
  
  
• Disconnect the long BIAS cable at the dewar end (connected to the RF feedthrough that connects to the bias board output), and plug the new cable in its place.
  
  
• Connect the other end of this long cable to a DB50-to-BNC breakout box and set it on top of the MUX rack (there should be some space available next to the lockin PSU)
  
  
• Using BNC cables, wire the BNC outputs of the breakout box to the BOTTOM row of BNCs on the CSO-DAS OPTOISOLATOR BOARD as follows:
  
  breakout box        panel (1st bnc is 1)
   2/18               2
   4/20               3
   6/22               4
   8/24               5
  10/26               6
  12/28               7
  
  
• There is a DB50-to-DB25 cable connecting the bias monitor DC lockin output to the DB25 input to MUX 12.  Disconnect the DB50 end from the lockin box and connect it to the BOTTOM DB50 connector on the CSO-DAS OPTOISOLATOR BOARD.
  
  
5. If you are using a Rev. 2 bias board (the serial number on the front panel will be 2.X): Flip the CLOCK switch on the bias board RIGHT (to EXT) and make sure there is a shorting cap on the adjacent BNC.  See the diagram on the side of the e-box.  This shuts off the bias generator clock.


6. Check that everything is basically working.  Start an IV curve going (see the instructions below to see how to put the board into DC bias triangle wave mode) and make sure you see signal on at least one channel in each hextant, the bias monitors, and the GRT on the DAS.  The channels to enter on the DAS screen for the various signals are:
   
   bolometers:     hex 1   DAS ch 32-55     (start at 32, )
                       2          96-119    (24 channels per hextant, each  )
                       3          160-183   (hextant offset by 64 = 2 x 32  )
                       4          224-247
                       5          288-311
                       6          352-375
   
   bias monitors:  hex 1    377    (yes, 377, not 376)
                       2    378
                       3    379
                       4    380
                       5    381
                       6    382
   
   RGRT: ch 56  = -(RGRT/200k)*10V
   
   Be especially sure that the hextant bias monitors and RGRT are being read correctlly; they are critical to the analysis.
   
   
7. Adjust the DC bias setting to get the proper range for the IV curve.  With the INT/EXT switch in INT mode (internal DC bias, not triangle wave), adjust the bias so the bias monitors read about -6 V.  Then flip INT/EXT to EXT mode to get a triangle wave and confirm that the bias monitors peak at ~-9V.  If the bias monitors saturate (reach -10V) then reduce the bias setting as necessary.  Note that the IV curve always has a flat section at maximum bias; do not confuse this with saturating the digitizer.
   
   
8. Turn the IV curve off:
   
   
   • Rev. 2 bias board: flip the AC/DC switch to AC
     
     
   • Rev. 3 bias board: set the rotary switch to "0V"
     
   
   
9. Run the BOLOCAM_SKYDIP_LOADCURVE macro as usual, but, if using a Rev. 2 bias board, exchange AC and DC everywhere the instructions tell you to flip the AC/DC switch.
   
   
10. When you are done, go back to normal cabling/bias mode.
    
    
• Cabling: simply reverse the above steps.  BE CAREFUL!  Miscabling may go undetected for quite some time, especially if you do something like exchanging the cables for different hextants.
  
  
• Bias board:
  
  
• Rev. 2 bias board:
  
  
  1. Flip the CLOCK switch on the bias board LEFT (to INT)
     
     
  2. Flip the AC/DC switch to AC mode
     
     
  3. The skydip instructions should have already instructed you to switch the INT/EXT switch back to INT mode, but double check.
     
     
• Rev. 3 bias board:
  
  
  1. Flip the AC/DC switch to AC mode
     
     
  2. Set the rotary switch to "0-5V"

• 2004/01/14 SG
  First version
  
  
• 2004/01/29 SG
  Add links to get back to main pages.
  
  
• 2004/01/31 SG
  Much more detail on power supplies and grounding in the cabling section
  
  
• 2004/02/04 SG
  Minor changes, add cabling instructions for DC bias skydip IV curves
  
  
• 2004/02/09 SG
  More detailed instructions for cabling of GRT analog monitor and CHOP_ENC, as well as for checking that correct lines are connected
  
  
• 2004/04/20 SG
  Some of the links were incorrect
  
  
• 2004/04/27 SG
  Some updates and additional info, add Rev. 3 bias board instructions.
  
  
• 2004/05/13 SG
  Add pictures.
  
  
• 2004/10/05 SG
  Put directions for adjusting triangle wave amplitude/offset for Rev 3 bias board on this page.  Correct directions for AC bias mode for Rev. 3 board.
  
  
• 2005/01/25 SG
  Correct discussion of VAR/FIXED switch for Rev. 3 bias board.  Indicate function of VAR/FIXED switch for Rev. 2 bias board.
  
  
• 2005/06/05 SG
  Minor corrections.