Table of Contents

Introduction

We plan to use 5V TTL signals throughout the KPF system to trigger various devices. These signals will be 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 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.

To solve this issue, we have decided to use 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 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:

In the above, the top Galil is called the “Shutter Galil”, as it was originally within the KPF system only to control two ‘source select’ shutters (see Appendix below).

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 Chief Technology Officer alamb@uniblitz.com
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

Appendix 1 - Source Select Shutters Test Setup

This diagram shows how the source select shutters were originally wired up during software development.

This was before SG noticed the 12V limit for the Galils, but despite the 5V source this system actually worked and Will wrote the software for this configuration and pins.

Note how each shutter is on a separate bank, since at this time these shutters where the only things attached to this Galil. The thought was that we might as well separate them just in case there is any cross-talk (although that fear was not based on any facts).

Also note how here the 5V source was used to supply power to both the shutter and the Digital Out Banks. The shutter datasheet shows that they can be powered from 5-12V, so in the wiring diagram above they are now being powered from 12V. This keeps the power draw on the 12V side of the voltage dividers, with only signals on the 5V side of the voltage dividers.

Appendix 2 - H&K Galil Test Setup

In order have a system available for Will to test software with, we made up an interim setup for the H&K system. This used a 5V power supply, which is supposedly too low for the Galil but worked in the above source select shutter setup above.