The Alternative Comparison Lamp Controller


1.  Introduction:

The WYFFOS Alternative Comparison Lamp Controller has been designed to switch a mains supply to three 13 amp. outlets controlled from a software interface equivalent to that found on the ISIS and UES comparison lamp controllers. From a software point of view the operation of a comparison lamp controller appears the same irrespective of which type of controller is being used with WYFFOS. The main purpose of the Alternative Controller is to provide a switching control point for comparison lamps which cannot be accommodated within the ISIS controller format Therefore any comparison lamp with its own mains driven power supply can be connected to an outlet and switched on or off from the either the Engineers, or Users interfaces.

1.1  Document history:

1.2  Version notes:

1.3  Mnemonics used throughout the text:

2.  Construction:

2.1  Enclosure:

The enclosure is a 2U 19" distribution panel which is fitted with 3 x 13 amp outlet sockets., plus a fuse and blanking panel all as BS1363 faceplates. Within the enclosure is a quad output solid-state relay and some circuitry to provide a status output for each mains outlet.

3. Circuit description:

3.1  Switching:

The main switching component is based around a quad output solid state relay which can be switched from an input voltage range of between 4 - 15v dc. Three of the relays are each connected to a 13A outlet socket. The fourth is used to enable the other three from the control input line on pin 25 on the 25W D connector. The neutrals are not switched and are commoned to the incoming mains.

3.2  Status outputs:

Status outputs are available on the 25D connector at TTL level which are derived from an AC/DC to logic interface opto-coupler connected to each 13A outlet. These devices have been configured to switch at a 230Vac threshold level and not be influenced by the off state voltage and current produced by the solid state relay. The 20K 6W resistor provides a minimum load to the relay should nothing be connected to the 13amp. socket. The relay off-state voltage is 38Vac. A low pass filter using the pull-up resistor 4K7 and 47f capacitor network ensures a constant logic level output from the opto-coupler. This signal is inverted and buffered (SN7416) to the output connector. The final logic level `1' indicates comparison lamp mains on. Logic level `0' indicates comparison lamp off. Unused status outputs are held `lo' as their off state, and linked connections 09 - 10 or 22 - 23 are used for the connection status loop.

4. Parts lists:

     Component        Manufacturer  Supplier &  No.    Cost per
                     & part number  order code  off    item

2U x 19" empty                          RS       1      28.00
distribution panel                    817-612

Single gang 13A         MEM 3002        RS       3      02.90
outlets                               487-211

Fused connection        MEM 3210        RS       1      05.93
unit                                  332-616

Blanking plate 1        MEM 3503        RS       1      01.20
gang                                  487-851

Solid-state relay,       Crydom       Farnell    1      48.00
quad output              TD24200      178-761

AC to logic              Hewlett      Farnell    3      02.77
interface Ic             Packard     HCPL3700

Buffer Hex inverting      Texas         RS       1      00.92
o/c Ic                    7416        306-364

Resistor  4k7 0.25W                     RS       3      00.032
M.F                                   148-663

Resistor 91K 0.5W                       RS       3      00.052
M.F                                   163-842

Resistor  240 0.25W                     RS       1      00.032
M.F                                   148-354

Resistor  20k  6W                       RS       3      00.74
Vitreous enamel.                      159-578

Electrolytic                            RS       3      00.126
capacitor 47uf 10v                    103-941

Decoupling cap.                     from stock   2      
0.1uF disc ceramic 15V

`D' connector 25W                       RS       1      03.75
plug solder (fixed)                   466-191

6A mains cable                      from stock  2m      
Mains cable                             RS       1      02.03
connector                             449-922
Reference data sheet    HCPL-3700       RS              
for logic interface ic.               F10029

Reference data sheet     TD24200      Farnell           
for solid state relay

5. Circuit diagram:

This is where a circuit diagram will be hopfully... Hmmm you must be bloody joking!!

Original Document alt_man.doc by H. M. Stevenson RGO Cambridge



Converted to HTML by M. A. Parr