Solved - How to run spring shutter with bi-stable driver for TAU - Page 1
Forum section: electronics / general

author: Logan
author_rank: Frequent Contributor
timestamp: August 16, 2023, 03:10:07 pm
content: Hi friends.I mixed bi-stable/iris type board with spring-return shutter on Flir TAU, and the shutter return before calibration completes, because the motor driver do not keep the power during calibration.There's 2 ways but I have difficulty on both.1. Modify the shutter to remove the spring: I cannot open the gear box because it's glued together.The friction won't be able to hold the shutter in place when idle.2. Modify the driver to make it keep the power when shutter closed: I don't know how to do that at all.So, do you guys have any ideas?

author: Fraser
author_rank: Super Contributor
timestamp: August 16, 2023, 11:16:32 pm
content: Take a look at the T-Type Flip Flop. It toggles its output state with each pulse on its clock input whilst the T input is held at logic 1.https://ecstudiosystems.com/discover/textbooks/basic-electronics/flip-flops/t-flip-flop/#:~:text=The%20toggle%2C%20or%20T%2C%20flip,flop%20holds%20the%20previous%20state.https://www.electronics-tutorials.ws/sequential/toggle-flip-flop.htmlIf your TAU board is using a polarity change for the FFC set and deset pulses you will need a bridge rectifier before the T-Type Flip Flop to ensure the pulse is always positive going for FFC set and deset (a polarity reversing FFC output often uses an H-bridge driver but I do not know the specifics of the TAU). You will need to consider input voltages and the need for a simple transistor based driver for the FFC solenoid. The whole circuit could be made very small if SMD components are used. It could be built with point to point wiring and no PCB, dead bug style and then encapsulated in epoxy if size is important.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: August 16, 2023, 11:23:06 pm
content: This cheap little module might be a good building block on which to base an adapter for your TAU ?https://www.ebay.co.uk/itm/255087318688It is triggered on the negative transition of the input but a signal transistor can be placed on the input to create a positive trigger capability. The output drive is ready for you to use. Remember to check the input voltage and any polarity reversal that is present. Adapt the little PCB to serve your needs… diode bridge input, potential divider etc.Fraser

author: Logan
author_rank: Frequent Contributor
timestamp: August 17, 2023, 05:32:08 am
content: Thank you very much Fraser.I was thinking about something similar but didn't even know what search keywords are.I will look into them deeper later.

author: Logan
author_rank: Frequent Contributor
timestamp: August 17, 2023, 03:37:05 pm
content: Another solution is to keep the power for a second after initial signal from TAU.How can I find a good quality module for either type?I really don't want to put a no brand Chinese part in by device.

author: Fraser
author_rank: Super Contributor
timestamp: August 17, 2023, 05:54:22 pm
content: Then you must build it yourself.Design a circuit that meets your needs. Design the PCB. Find a USA based PCB fabricator and have them make the PCB. They may, or may not offer a PCB component population service. If not you will be soldering the SMD components but they are not complex. The function you need may be provided by simple glue logic IC’s and transistors.Creating a T-Flip Flop has the issue of if a glitch occurs, the flip flop will go out of sync with the required function. To create a set period of power to the FFC solenoid from a simple initiation pulse requires a simple monostable pulse stretcher. There was a thread on this forum discussing such. A simple 555 timer or discrete transistor circuit may be used. The mono stable approach avoids the issue of a glitch causing issues but do be aware that some thermal cameras operate the FFC solenoid several times in quick succession when booting and warming the microbolometer. You need to ensure your mono stable is either multi event responsive or has an adequately short duration to match the true needs of the FFC events.https://www.eevblog.com/forum/beginners/pulse-extender-circuit/All of my solutions are ‘bush engineering’ and not really how this problem should be solved. More elegant solutions would become more complex for you however. Some might even dedicate a tiny ARM processor to the task !Fraser

author: Logan
author_rank: Frequent Contributor
timestamp: August 18, 2023, 04:11:20 pm
content: Thank you Fraser.I may disappoint you because I solved it with a stupid solution.I attached a magnet to the shutter arm, and another one to the case.So when the shutter is closed, the magnets keep it closed.When it want to open, the reverse force from the motor make it open.I know it's stupid, but it does work well.

author: Fraser
author_rank: Super Contributor
timestamp: August 18, 2023, 08:54:09 pm
content: A perfectly sensible ideaThat is, after all, how many bi-stable shutters operateI am pleased that you were able to apply the technique to your TAU shutterFraser