Introduction
We plan to use 5V TTL signals throughout the KPF system to trigger various devices to open and close shutters, and to control CCDS (start acquisition, start readout, etc).
One issue with this is that the Galil RIO 47142 controllers we have already purchased 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.
We have decided to use 12V-to-5V voltage dividers for the signal lines, placed between the Galil outputs and the various devices. Voltage dividers were chosen as they are analog and therefore should not impact the signal timing.
Relevant Sections from the Galil Manual:
Pin Designations (from Galil Manual, page 97):
Schematic Layouts for TTL-based Devices in KPF
In the above, the top Gail is called the “Shutter Galil”, as it was originally within the KPF system only to control two ‘source select’ shutters. In the new scheme these shutters would also
Note that not shown on the diagram above are two other shutters that will be connected to this same basement Galil as shown below.
Given these shutters also d
HK Galil Schematic
How the HK Galil is currently wired up. Here it is using only 5V as the external DO bank source, as a placeholder until the 12V voltage divider scheme can be implemented.
The Archon situation shown above is more complex, but it would be ideal if the Archon PCB could be utilized here as well. Note
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 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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