Michael:
I am not a buyer but I am an admirer:
In a now ancient time I knew a lot of really very gifted engineers who had
never learned that “technically sweet” is not the goal. Salt with a
little political job keeping and thus the American space program….
Bill
On Mon, Feb 7, 2022 at 6:25 PM Michael Clive <zeinin@xxxxxxxxx> 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.
