Table of Contents
Introduction
5V TTL signals are used throughout the KPF system to trigger various devices. These signals are used to open and close shutters, and to control CCD time-sensitive operations (start acquisition, start readout, etc).
One issue with this scheme is that the Galil RIO 47142 controllers cannot use voltages less than 12V on their Digital Out (“DO”) lines. Furthermore, as shown below, the various devices being controlled cannot accept voltages higher than ~5V for the Trigger In signals.
To solve this issue, we employ 12V-to-5V voltage dividers on each signal line, placed between the Galil outputs and the various devices. Voltage dividers were chosen over semi-conductor options as they are analog and resistive-only (no capacitors) and therefore should not delay or otherwise impact the signal timing.
Relevant “Digital Out” Sections from the Galil Manual (page 42)
Start of “Digital In” Section from the Galil Manual (page 48)
More follows in the manual.
Pin Designations from the Galil Manual (page 97)
Schematic Layouts for TTL-Based Devices in KPF
Simplified Layout for time-sensitive devices:
Combining everything together leads to the following wiring diagram. Back-illumination LEDs are also included here as a way to simplify their connections, in that their cabling could be included within the source select shutter cables.
Details on resistors - only Archon ones were changed
The same Galil model is used for the Ca H&K exposure control. Since similar (and fewer) devices are being controlled by the Galil for that system, the same 12V-to-5V adapter PCB was utilized, with just some of the pins going unused.
Details on resistors - all were changed
TTL Details per Device
Description | Device | Notes |
|---|---|---|
Shutter Controller | Uniblitz VED24 | Screengrab from VED24 manual:  Note the VED24 manual is somewhat confusing about what the PULSE INPUT trigger needs. I clarified with Uniblitz and they replied with this description: “When the input signal goes Low [0V], the shutter will Open . The input signal should stay Low[0V] for the duration of the desired exposure time and be at least a minimum duration of the pulse width needed to make sure that shutter will properly ‘Open’ for the VED24. In the case of the DSS25B series shutter the minimum exposure pulse would need to be greater than 35ms. When the input signal is removed and/or return to the High[5V] state the shutter will close. The shutter will stay in the Close position until the Pulse Input signal goes Low[0V]. The VED24 Driver, when configured for the appropriate shutter device, will provide the fixed pulses need to ‘OPEN/CLOSE” the bi-stable shutter. Let me know if I can be of any further assistance.” Regards, Adam J. Lamb |
Ca HK Detector | Andor Newton | Screengrab from Andor Newton manual:  |
Archon Controller | STA Archon | From the Archon manual: “The Trigger In circuit is shown in Figure 4. A 3.3V input at 2 mA is sufficient to trigger the optoisolator. Inputs up to 10V are tolerated.” |
Exposure Meter | SBIG Aluma 47-10 |  |
Max Signal Voltages Allowed by TTL Devices
Description | Device | Max Signal Voltage | Source |
|---|---|---|---|
Shutter Controller | Uniblitz VED24 | 5V DC | Email from Uniblitz: Steven, It would be recommended to use 5VDC for the TTL ‘High’ and 0VDC for TTL ‘Low’ when interfacing to the VED24 drive controller’s Pulse Input BNC. Regards, |
Ca HK Detector | Andor Newton | 3.3 to 5 V DC | Email from Andor: Hi Steve, 12 volts will damage the external trigger. Please use between 3.3 to 5 volts TTL. Kind Regards, |
Archon Controller | STA Archon | 10V DC | From the Archon manual: “The Trigger In circuit is shown in Figure 4. A 3.3V input at 2 mA is sufficient to trigger the optoisolator. Inputs up to 10V are tolerated.” |
Exposure Meter | SBIG Aluma 47-10 | 5.5V DC | From the Aluma manual: “CAUTION: The Trigger In input voltage must not exceed 5.5V maximum.” |
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