Michael,
I respect your point of view (and thanks for the link, I hadn't seen it
before) but I guess I have a different perspective. My first question
when working on something new, especially hobby-related, is "what new
skill can I learn?" Yeah, it took me forever to build a flying liquid
rocket but along the way, I taught myself how to run a mill and lathe,
lay out circuit boards, solid modeling, 3D printing, fluid systems,
cryogenics, etc. I already had a background in aerospace testing and
hardware/software but I was able to shore up my skills in RTOS design,
calibration, and instrumentation by building and debugging my own
stuff. Almost everything I learned on the rocket project has been
applicable to my other endeavors. I always told myself that I was
building capability, not just a rocket. I agree though that sometimes
you can get carried away with the NIH syndrome but it depends on what
your goals are.
-Bob
On 2/7/22 19:25, Michael Clive wrote:
Hey all, eleven years ago when I got into experimental rocketry, I thought that a rather big problem to solve was how to get hobby microcontrollers to safely actuate big solenoid valves. I now know that one can easily sidestep this problem by using PLCs and relays for your GSE, but hey, I don't think telling 26 year old me that would have changed anything.
Anyway, myself and a friend went ahead and designed a circuit board around a DRV104 solenoid driver chip. My friend did an excellent job with all of the hard work. I think all I did was say "Me need chip make valve move no break arduino", and they designed an entire board/layout and made the first one.
https://www.ti.com/product/DRV104
"The DRV104 can be set to provide a strong initial solenoid closure, automatically switching to a soft hold mode for power savings. The duty cycle can be controlled by a resistor, analog voltage, or a digital-to-analog (D/A) converter for versatility. The Status OK Flag pin indicates when thermal shutdown or over-current occurs."
We made it pretty fancy. It is fully optoisolated. All parameters are tunable on the board, if you install all the caps.
Good news: Giving this stuff away to whoever needs it more than I do.*
Bad news: There is only one complete driver. The rest is PCBs and parts. Since my friend, the EE who designed it, is an EE, they made it with surface mount components rather than the through hole parts that us barbarians prefer. I believe there are parts to make 24 more. I want to make
Here are photos:
https://photos.app.goo.gl/u5zqtgDWmq4Q9Yzy7
Now, what are the lessons here:
The XY problem is /real. /
https://xyproblem.info//
/
If you are neophyte to any field, be vigilant against this. What I should have been doing was asking "What is the minimum effort, minimum capital solution to building a GSE control system", not "What kind of cool PCB can I design to control stuff with an Arduino". If I had actually done the work and study to figure this out, I am certain I would have discovered Automation Direct and the BRX plcs. The same $1k I spent on this project could have gotten me a decent PLC setup that could control whatever test stand I wanted in an easy to use, safe way.
In short, I tried to solve the cool problem, not the real problem.
With that being said, if you do need to swing valves or heaters with a uC, this is a pretty nice solution!
*Please pay shipping or pick it up locally here in the Bay Area.
