Re: Sprinkler pump controller
- From: ehsjr <ehsjr@xxxxxxxxxxxxxxxx>
- Date: Sun, 18 Mar 2007 21:46:26 GMT
jfma@xxxxxxxxxxxxx wrote:
I've had this idea for a while but don't know exactly how to go
about it. I'm thinking of a micro controller of some sort but I
haven't worked with micro controllers and not sure which one would be
best for this project. I also want to make this project into
something that I could use on a resume, something . I am an
electronics engineering technician (AS-ET).
This is the basics of what I have now. I have a water retention
system (55 gallon drums manifold together) that has an MPXV501GP (1.45
PSI) to detect the water level in the system. I have a rain sensor
mounted on the gutter.
What I want to be able to do is to turn on the sprinkler pump
after it hasn't rained for a number of days. I also want the pump to
come on when the system level goes above a narrow high window and off
again below that same window. I also want it to shut down the pump if
it goes below a bottom window and able to come back on above that
lower window when it hasn't rained for the preset number of days.
Upper and lower windows could be detected with 2 op amps for the
upper and 2 for the lower. I've done something similar to this before
but was a number of years ago and I can't find the documentation as to
what I did and parts I used. They probably don't make those parts
anymore anyway.
The newest data book I have is a TI linear volume 3 from 1992. Do
they have hard copy data books any more or they all on CD?
"Program" it first at the functional level, before choosing
the ucontroller. Two conditions do not "go through" the
ucontroller: When the low window bottom sensor is dry,
the pump is off regardless of any other conditions; when the
high window high sensor is wet, the pump is on regardless
of any other conditions. That said, you still might want
to have the uc look at them for errors, like the low window
low sensor dry but the othere window sensors wet. Once you have
laid out all the functions you want you should be in a better
position to pick the uc. But it really doesn't matter, as
you indicated that you haven't worked with them.
So, what you really want is someone to provide a complete
solution, with the uc already chosen and the code written,
or someone with experience to tell you which uc to use so
that you can then learn how to use that particular uc
family. That experienced person will be better able to
meet your needs after you have spelled them out. For example,
you did not address resetting the timer, error checking
the sensors, what to do if the pump is running and it starts
raining, whether the timer needs to run during a power failure,
what the power on reset state should be and who knows what else.
I'm having a hard time figuring out how this project
demonstrates the need for a uc, but I think you could
demonstrate the parts cost advantage of one.
I'll show a hardware solution below. The purpose is
really background to show that the person reading the
resume may think "why in the hell is he showing such
a simple use of a uc, when so much more could be done?"
Excluding the timer, a simple hardware solution is a couple
of relays. I'll draw the comparator outputs as switches (saves
drawing the op amps) All switches made when wet.
Your rain sensor (RS - on when wet) :
/
+ ---o o---+---> timer start on break (-)
RS |
[R]
|
Gnd --------+
Your low window level top of window (TW) and bottom of
window (BW) sensors (on when wet):
/
+---o o---o--- < Low Relay 1 point
| BW ^---+
| |
| / |
+ ---+---o o----------+
TW |
[Low Relay]
|
Gnd -------------------+
When the tank is filling, BW closes first as the
level rises. When the water reaches the top
of the window, TW closes and the relay energizes.
It stays energized, if the water level drops, until
BW opens.
Your high window level top of window (TW) and bottom
of window (BW) sensors (on when wet):
/
+---o o---o--- < High Relay 1 point
| BW ^---+
| |
| / |
+ ---+---o o----------+-------< from timer output
TW |
[High Relay]
|
Gnd -------------------+
Operates the same as the bottom window sensors.
In addition, the relay can be controlled via the
timer. That meets your condition of the pump
operating when the timer calls for it, regardless
of the status of the upper window sensors.
AC ----- < Low Relay 2 Point
^------+
|
+--- High Relay 2 Point
+--^
|
[Pump]
|
AC -----------+
The point of all that is to show that the uc
is not providing a whole bunch of function that
mandates its use over hardware. You want the
resume to sell a product - you - to the company.
Maybe it would be sufficient for your project to use
the uc as the basis for your timer - I don't know. It
seems to me a waste of uc power to use it only as a
timer in this. Neither the hardware nor software solution
can be given until timer reset is defined, but the
hardware solution might be a counter like a CD4060
and support components or maybe cascaded ICM7242's.
I think it would be a better project if you could do
all the "thinking" with a uc - and show enough need
for "thinking" that the person reading the resume
is impressed. As stated, your project doesn't do that,
in my opinion.
Suggested additions: add zones, with individually
selectable on times like 4 hours every other day
or so many minutes daily or once a week or whatever,
sensor logical error checking, maybe an "it's been
too dry for too long" alarm to a human operator, etc.
The more practical flexibility you put into it, the
better.
Ed
.
- References:
- Sprinkler pump controller
- From: jfma
- Sprinkler pump controller
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