OD Information - JLC Enterprises, Inc.
Contents
1. Install in the same manner as above making certain that the banded end of each diode is oriented as shown in Fig 2 Note that the banded ends of these fast Schottky barrier rectifiers special glass diodes are sometimes hard to see Take special care in locating the band and if required use a magnifying glass to double check the band orientation S1 Making certain that you have all 14 pins located properly in their respective holes with the correct orientation for Pin 1 hold the socket tight against the board as you solder the pins If you are not sure of the correct orientation for Pin 1 see Fig 1 7 of the V3 0 User s Manual As with any multi pin part solder only a couple pins first those on opposite corners of the socket Reheat as necessary to make certain that the socket is firmly against the board then solder the remaining pins S2 Install this 5 contact side entry connector by first hooking the nylon retaining fingers over the card edge then feeding the metal contact pins through the card holes Make sure all five pins pass through the holes Hold the connector shell tightly against the card as you solder C1 C5 C6 Insert these components with the capacitor standing perpendicular to the card solder and trim the leads C2 C3 C4 These capacitors tend to look alike so separate out C2 first so that it doesn t get mixed up with C3 and C4 Then insert these components with the capacitor standing perpendicular to t2. in the Testing Detector Operation section as included as part of this Web site In particular using the clip lead and LED assembly connected directly to the detector output is important because simply observing correct operation of the LED built into the detector DOES NOT verify that the overall detector is operating correctly The OD card layout uses wide traces and spacing between traces so soldering problems should be minimized There are only two active components the IC and the transistor so debugging is easy particularly because the IC 1s fitted in a socket CONNECTIONS TO ODMB WHEN USING OD Fig 3 shows how to connect ODMBs when using the OD Simply run the detector power bus to each ODMB whether located together or distributed around your layout To S rail power source e g cab selector switch if using MBC or cab relay card if using CCC or booster if using DCC S rail BK 1 BK 2 N rail Vout for BK 1 Vout for BK 2 Only portions of ODMBs shown we A A is up 12Vdc eee We cal communes cs Se supply Ed 12Vde ODMBs Fig 3 Connecting ODMBs when using ODs To power the ODs you need a power supply that provides both 12 Vdc and 12Vdc regulated outputs as well as ground Most surplus computer power supplies provide these three connections as well as 5 Vdc For connecting the detector s output V ouw to different devices such as lamps LEDs relays and C MRI inputs consult the Optimized Occupancy Dete
3. For example even with an obviously strong shift to DCC JLC Enterprises continues to fill orders for the OD albeit at this stage the DCCOD probably outsells the OD by a 4 to 1 margin Consequently there remains a good market for second hand fully functional ODs By using Ebay and or contacts obtained through the C MRI User s Group many users converting from DC to DCC have very successfully sold their ODs and put the proceeds toward purchasing new DCCODs Baseline pricing for ODs has a very wide range and depends on if they are purchased as kits for an estimated price of 15 or as completely assembled and tested estimated at 25 For the Do It Yourselfers purchasing the OD board from JLC at quantity discount and the electronic parts from each of the recommended suppliers again at quantity discount the estimated cost can be as low as 8 to 9 but more typically at 11 to 12 for low quantities Averaging all these prices together t would appear that a reasonable rather quick to sell price for a used assembled and tested OD would be about 10 to 15 each Basically this sells the detectors at an averaged cost level for the board plus parts but with nothing charged for the assembly time Applying that amount toward a Do It Yourselfer s version of the DCCOD basically covers the cost of the boards pulse transformer and electronic parts assuming all were purchased at quantity discount In summary Do It Yourselfers who purchase boards d
4. where polarity of assembly is important As a further aid to assembly the positive pad for polarity sensitive capacitors the LED and pin 1 of the IC socket are square Also the longer lead on capacitors and the LED is the positive lead Once you have one OD assembled and operating correctly you can use it as a pattern for assembling additional cards Table 3 1 Optimized Detector OD Rev K Parts List in order of recommended assembly Qnty Symbol Description R1 10Q resistor brown black black R3 R5 10KQ resistors brown black orange R6 3 6KQ 1 2 W resistor orange blue red R9 2 2KQ 1 2 W resistor red red red R10 10KQ resistor brown black orange R11 2 2MQ resistor red red green R12 220KQ resistor red red yellow R13 330KQ resistor orange orange yellow D1 D2 For regular DC or AC track power select from 3A 50V diodes Mouser 625 1N5400 E3 6A 50V diodes Mouser 625 G1750 For command control e g DCC or Railcommand select from 3A 40V fast recovery diodes Mouser 625 GI850 5A 50V fast recovery diodes Mouser 625 GI820 _ N S DW 2 D4 D5 1A 100V diodes 1N4002 Jameco 76961 2 D6 D7 Fast Schottky barrier rectifiers Mouser 625 SD103C 1 S1 14 pin DIP socket Jameco 112213 1 S2 5 pin Waldom side entry connector Mouser 538 09 52 3051 3 C1 C5 C6 1uF monolithic capacitors Jameco 332671 1 C2 1 5uF 35V tantalum capacitor Jameco 545713 2 C3 C4 2 2uF 35V tantalum capacitors Jam
5. OD TRACK OCCUPANCY DETECTOR By Bruce Chubb If your railroad is pure DC then the best detector to use is the straight DC Optimized Detector the OD In fact for DC railroaders installing the JLC provided OD cards is a great way to start building toward a more complete computer interface You can use ODs to indicate occupancy status of hidden trackage to drive LEDs on your track diagram as trains progress around your layout to control grade crossing signals and to control automatically the polarity in reverse blocks With detectors installed it s a natural step forward to use the C MRI for signaling Although I strongly recommend using ODs for DC based railroads if you are starting from scratch on a DCC equipped railroad I recommend using the newer special DCC version of the OD the DCCOD If this is your situation you may wish to simply focus on the downloadable material covering the DCCOD OCCUPANCY DETECTION WITH DC The originally designed OD was created specifically for railroads using straight DC In fact I consider the detector so good that I call it the Optimized Detector My friend Paul Zank who is an N scale model railroader and an award winning aerospace electronics engineer helped in its design Here are a few of its important properties e Its sensitivity is easy to adjust with a trim potentiometer e ts built in turn on delay of 25s and turn off delay of 3 5s greatly reduces problems from dirty track and other causes
6. Therefore I will cover this recommended approach in more detail shortly On the other hand many C MRI users have retained their ODs when converting to DCC and have found the results to be very satisfactory This is especially the case if the switch to DCC is for a smaller application that uses a single DCC booster Multiple DCC booster applications retaining the ODs do result in added system complexities 1 e unless the brand of booster happens to include or is able to be modified to include an optoisolated control bus connection Most DCC boosters do not provide for this capability The next chapter details the DCCOD Then in Chapter 5 Using the C MRI with Digital Command Control I go into detail showing the application of both the OD and the DCCOD to DCC layouts Exploring the application of both detector types and observing the pros and cons of each approach should help in making the decision whether to keep the ODs with DCC or to start anew using the DCCODs If you have no interest in DCC and thus no interest in the DCCOD please feel free to skip ahead to Chapter 7 covering Turnout Control Otherwise before we move forward let s just take a moment to close out this chapter by taking a look at selling existing ODs to pick up DCCODs SELLING ODs TO PURCHASE DCCODs Although many may feel that DCC has taken over the whole railroading community if you really analyze the situation there is still a very strong base of strictly DC users
7. ction writeup included in this Web site SETTING DETECTOR SENSITIVITY One of the greatest attributes of the OD is its super high sensitivity and we will see shortly why this property is so tremendously important when applied to straight DC train control To take full advantage of this capability we need individually to adjust each OD to as high a sensitivity setting as can be achieved without it being so high that it will respond to the leakage resistance between the two rails thereby falsely indicating a clear block as occupied Such indications are frequently referred to as false occupieds Adjusting each detector to reach this optimum sensitivity setting requires two simple steps 1 With the OD installed and wired to its appropriate block and with the block clear turn the detector s sensitivity adjustment potentiometer fully clockwise This should cause the clear block to show up as occupied 2 Then rotate the potentiometer back counterclockwise until you just reach the point where the block shows up as clear i e the test LED on the detector goes dark and then continue the counterclockwise rotation for another 3 to 5 degrees That is all there is to optimally set detector sensitivity Repeating the procedure for each detector will result in you achieving the maximum possible usable sensitivity for each section of detected track on your whole railroad Pretty neat huh Now let s dwell just a moment on each of the t
8. eco 33734 1 R2 10KQ potentiometer Jameco 94714 1 Q1 2N4401 small signal transistor Jameco 38421 1 L1 Red diffused size T1 LED Jameco 333850 1 U1 LM339N quad voltage comparator Jameco 23851 Author s recommendations for suppliers given in parentheses above with part numbers where applicable Equivalent parts may be substituted Resistors are 14W 5 percent unless otherwise noted and color codes are given in brackets Note R7 R8 and D3 are not used with OD Rev K Because this may be your first card assembly I ll go into more detail in the following assembly steps R1 R3 R13 Make 90 degree bends in the leads of each resistor so it is centered between its two holes and the leads just fit Insert and solder while holding the part flat against the card then trim the leads Note that R2 is a potentiometer to be installed later R6 and R9 are 12W resistors and R7 and R8 are not used with the Rev K detector D1 D2 Use needle nose pliers to bend the heavy leads of these power diodes at right angles so they drop into the holes The banded ends must face in opposite directions as shown in Fig 2 Slip a 1 8 in spacer between the card and the diodes as they are soldered then remove the spacer The space helps ventilate the diodes and protects the card D4 D5 Install in the same manner as above making certain that the banded end of each diode is oriented as shown in Fig 2 Note that D3 is not used with the OD Rev K D6 D7
9. es to card edge distance Loner lead is plus Fig2 Parts layout for optimized detector Rev K Ready to assemble OD circuit boards are available from JLC Enterprises or you can purchase either complete kits or assembled and tested boards from EASEE Interfaces Do It Yourselfers assembling a large number of detectors using boards purchased from JLC Enterprises and then providing their own electronic parts can achieve costs at around 8 to 9 per detector With smaller quantities a more typical cost is 10 to 11 per detector Purchasing complete kits from EASEE Interfaces the cost is 15 each and assembled and tested 25 each Typically the kit route is the most economical approach for a small number of cards Also purchasing kits saves time from not having to place orders for electronic parts plus it saves on shipping and handling charges and minimum quantity fees which can mount up very quickly to 30 or significantly more when ordering from multiple suppliers For those wishing to assemble their own the basic skill required is PC card soldering If this is new for you make doubly sure that you have thoroughly digested the information on PC card soldering in Chapter 1 of the C MRI User s Manual Although the order of parts assembly is not critical but for the sake of having a plan I do recommend that you follow the steps in order and check off the boxes as you complete each one I ve included a after the symbol for each part
10. he card Make sure that the leads the longer of the two leads and denoted by a small sign go into the holes as shown in Fig 2 Incorrect polarity will damage these capacitors Solder and trim the leads R2 Install this potentiometer as in Fig 2 push the three prongs all the way into the holes as you solder You may need to adjust the back single prong a little so the potentiometer dial stands up perpendicular to the card Q1 Spread the leads of this transistor slightly to fit the three holes making sure the center base lead goes into the hole closest to P1 and that the flat side of Q1 faces the direction shown in Fig 2 Push it in only far enough to fit snugly without stressing the leads Solder and trim the leads L1 Note the orientation of the flat side and hole longer lead in Fig 2 With needle nose pliers hold the leads securely next to the housing and bend at right angles as shown in Fig 2 detail The LED sticks out over the edge of the card so you can see it when the detectors are plugged into their motherboard Once they are bent and properly fitted to the cards solder and trim the leads U1 Insert the LM339 IC making sure you have the correct Pin 1 orientation and that all pins go into the socket If unsure of the correct procedure for inserting and extracting ICs see Fig 1 7 in the C MRI User s Manual That completes the assembly steps for the OD To test your detector follow the procedure defined
11. ion is shown in Fig 1 Readers seeking details concerning the earlier Rev J version of the OD or how to update Rev J detectors to Rev K should consult Appendix D The track current capacity of the OD is determined by diodes D1 and D2 For most DC applications I recommend 3A diodes that have a surge capability of 50A If more is required you can substitute 5A 6A or 10A diodes 12Vdc or 12 24Vac bias ee Add 2 2K 2W bias resistor if track power can be removed i e with cab control 12Vdc 1 V TRACK OPEN COLLECTOR OUTPUT Connect through load pull up resistors etc to power supply N 1997 Bruce A Chubb GND Fig 1 Optimized detector schematic Rev K The OD Rev K is an update from the previous classic Rev J design The Rev K includes several improvements submitted by David Gibbons the creator of the C MRI User s Group The changes also reflect modifications suggested by Rich Weyand the owner of TracTronics and a frequent contributor to the C MRI User s Group to move the power supply decoupling capacitors previously located on the ODMB to each OD The main advantages provided by the Rev K modifications are increased sensitivity more operational independence from unbalance between the 12Vdc supplies and power input decoupling capacitors enabling detectors to be mounted remote from the detector power supply without the need to add the two 2 2uF capacitors on the ODMB as explained in Append
12. irectly from JLC with a discount and similarly purchase parts from the recommended sources again at a discount can basically just about break even when exchanging ODs for DCCODs that is if you disregard your assembly and test time Because of the true superiority of the DCCOD over the OD when applied to DCC railroads I really recommend that the above approach be given serious consideration by anyone having ODs now planning on switching to DCC
13. ix D For both Rev J and K the product of R11 and C2 determines the turn off delay and the product of R13 and C2 determines the turn on delay as long as R13 is considerably smaller than R11 Thus delay times can be changed as desired I enjoy the rather long 3 5s turn off delay which helps to solve the problem of intermittent contact as well as simulating the massive slow moving relays in prototype detection circuits The value of R6 can be varied to select the level of detector drive capability I selected 3 6kQ for reasonably high drive capability from the output transistor to handle loads as high as 3A and still maintain a good logic low for TTL connections For example I ve used a single detector to drive parallel loads of 10 LEDs and 4 TTL logic gates a total load of about 2A but still with a logic low around 7Vdc Reducing R6 to a lower value such as 1kQ would take more current from the power supply but would allow driving output loads up to 3A at 40V the ratings of the 2N4401 transistor For values of R6 of 3 6kQ or lower use a 12W resistor ASSEMBLING THE OD REV K Figure 3 2 shows the parts layout for the OD Rev K and Table 3 1 lists the parts required e Jes e Ra a g 02 cz 12Udc J Ea ae ER yas ny a a Ne D4 65 D5 aa 1997 2000 Bruce A Chubb D je 89 Clockwise rotation Mi increases sensitivity Yr Flat gt gt R2 trim pot Bending LED leads D INE hol
14. of intermittent contact e ts monitor LED is activated before the time delays giving instant occupancy indication to help in setting sensitivity e It has only two active components one IC and one transistor so it s easy to debug and maintain e ts open collector transistor output allows easy connection to LEDs TTL logic circuits relays and C MRI inputs e Jt works with conventional DC AC pulse power sound systems and all forms of command control including DCC However if you are not already OD equipped then selecting the DCCOD is the preferred choice for all pulse type command control systems including DCC e The design handles tolerates currents from microamps up to three amps and more if you substitute higher current diodes e Ifsa small modular unit one per block so it is ideal for plug in circuit card construction This eases system debugging and maintenance but alternate connection methods are also provided e Its price is very reasonable Assembling your own ODs where you purchase your own parts at quantity discount costs approximately 8 to 9 per block for a medium to large size layout At reduced quantities the cost for Do It Yourselfers increases to approximately 11 to 12 per block Tens of thousands of these Optimized Detectors ODs have been placed in service around the world and experience shows their performance to be exceptional OD REV K SCHEMATIC The OD s schematic for the newest Rev K vers
15. that when set to its maximum value it will always respond to the leakage resistance between the rails to indicate a clear block as occupied This is exactly the approach taken with the OD as well as the DCCOD Using this approach you are assured that track conditions are what is limiting the detection sensitivity and not the detector s design As we saw in Chapter 2 the leakage resistance between the rails can have a very wide variation depending upon such factors as what you use for ballast and roadbed what glue you use any foreign material that creeps into the ballast the cross tie material the humidity level and very importantly the length of the block being detected To take full advantage of every situation with the sensitivity of each detector set to its maximized useful level all the user needs to do is back off the sensitivity setting until it is fractionally below the level that indicates a clear block as being occupied For each given set of track conditions you just can t get a better sensitivity setting USING ODs WITH DCC Using the DCCOD is far superior in its application to DCC railroads when compared to using any of the diode type detectors including the OD Therefore I really wish that I could convince every user that is switching over from DC and using the ODs to sell the ODs and use the proceeds to obtain DCCODs I have talked to many C MRI users who followed this advice and they too now recommend this approach
16. ting for every detector should be about a 3 to 5 degree turn counterclockwise from the point where an unoccupied block shows up as occupied Such settings yield maximum possible sensitivity response to blocks actually becoming occupied Fig 4 demonstrates the sensitivity range of the OD as a linear function of the potentiometer position 1M s Power CTC 16 Pat 900K22 No bias resistor Book e oS Values on this 7 i 700KQ g 9 side of curve don t sooko 4 3 activate detector Measured F points with SOOKS2 5 PA 10K trim pot nr i 400KQ i y A A 300KQ x 2 200KQ Pa Values on this side of i curve activate detector l aac oe Pot at 10K 255 0 40 80 120 160 200 240 TRIM POT POSITION in degrees clockwise Fig 4 Linear control of detector sensitivity With the sensitivity potentiometer set to maximum fully clockwise the detector triggers with 1mQ or less across the track Set to minimum sensitivity the detector requires 1kQ or less across the track before the detector activates Thus the OD s potentiometer provides a 1000 to 1 linear range in sensitivity adjustment Now let s take a look at why setting detector sensitivity to its maximum possible value for every section of detected track is so very important NEED FOR BUILT IN SENSITIVITY ADJUSTMENT The only way to insure that a detector can be pushed up to the limit of useable sensitivity is to design the detector with super high sensitivity such
17. wo steps Step 1 sets the detector to its maximum possible sensitivity level which with the OD and the DCCOD is typically so high that the detector responds to the leakage resistance between the two rails causing the false occupied condition If this full clockwise setting maximum sensitivity does not result in lighting the detector s LED then either the detector itself is faulty or the leakage resistance of your block is extremely high which results in an extremely low value of leakage current in fact so low that even the OD can not detect it The latter condition has been reported by C MRI user Dave Gibbons to exist under extremely dry climate conditions To take advantage of even greater detector sensitivity under these conditions Dave increased the value of the R2 potentiometer from 10kQ to 50kQ If you suspect a detector problem then you can check its functionality and measure its actual sensitivity following the procedures defined in Chapter 2 Assuming that Step 1 lights the LED then what we accomplish in Step 2 is to reduce the detector s sensitivity so that it is just fractionally below the level of responding to the leakage resistance You just cannot do better than this when setting optimum detector sensitivity If over a period of time you find that a particular detector shows a clear block to be occupied simply rotate its sensitivity potentiometer fractionally more counterclockwise To summarize the normal set
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