This module is used to drive either our shutter or our filter
changer assemblies. It provides the power to operate the rotary solenoid in
either of these assemblies. The nominal operating voltage of the solenoid is
12V, but the module provides an initial voltage of 30V, falling back to a
holding voltage of 5V. This provides both faster switching and less
steady-state power dissipation than could be achieved at the nominal operating
voltage.
Operation of the module is very straightforward. It can be controlled either by the left-hand switch on the front panel or by an external control pulse. For control by the front panel switch, the right-hand front panel switch should be in the upper (int) position. When this switch is in the lower (ext) position, the module is controlled by the voltage applied to the (in)put socket. This is a standard TTL input, so the nominal input voltage range is 0V to +5V.
The normal state of the module is for the solenoid to be unenergised, and this corresponds to position (1). When the module is in this state, the left-hand (red) indicator is illuminated. In position (2), the solenoid is energised and the green indicator is illuminated. When the module is controlled by an external signal, position 1 corresponds to a low (0-0.5V) input voltage and position 2 corresponds to a high (3-5V) input voltage.
When the module is controlled by an external signal, position 1 corresponds to a low (0-0.5V) input voltage and position 2 corresponds to a high (3-5V) input voltage.
Regardless of the method of control, the (out)put socket provides a TTL-level signal which indicates the logical state of the module. A jumper link on the circuit can be used to change the polarity of this signal. When the jumper is in the normal position, a high output corresponds to position 2, whereas setting the jumper in the invert position makes a high output correspond to position 1.
The output socket allows one module to control another if required, by connecting it to the external input of the other module. The output inversion option allows the second module to be driven in antiphase to the first. This facility is provided because it is possible to connect a second solenoid to either the shutter or filter changer assemblies, to give active drive in both directions (in the normal configuration with one solenoid, return is by a spring). In this configuration, the two solenoids must be driven in antiphase, so that only one is on at a time. Using two modules connected as described above meets this requirement.
