help with pump control

Radio or laser link?. A transmitter intended for radio controlled models would work if fitted with a directional aerial. If you have line of sight then an optical link using a modulated laser pointer is theoretically possible but 400m is a long shot.

I've just been looking at :

will go up to a Km or so, but does not have FCC approval

google for ISM and licence free radio

martin

I think that aiming will be the hardest part with a Laser. You could get that sort of range with a modulated light bulb. Here's what you do for either laser of lightbulb:

At the transmitter end you make an open ended box, lets say 10CM on a side. The insides of the box are painted with the flattest black paint you can get. The light is placed at the center of this box. This makes an easy target to line the receiver up on.

The transmitter pulses the Laser at, lets say 500Hz. It uses a crystal oscillator for timing.

At the receiver, you use a telescope to make the image of the inside of the box fall onto a photo detector.

The receiver electronics has an amplifier and lets say the dreaded PIC or an 8051 with ADC. The amplifier contains a modest band pass filter. The micro runs on a crystal so that its timing is very good. Creating a bandwidth less than 1Hz isn't hard to do in a micro.

How large is the holding tank? If it is able to contain sufficient water for several days of use then you only need to top it up once a day.

A system I used in our previous house (in the Scottish Highlands) was to install a ball valve in the receiving tank and a pressure switch in the pump drive pipe. When the pressure at the pump rose above a preset level the pump turned off. It stayed off until the next day. I used a timer but, since your pump is solar powered, you could use a relay to hold the pump off. The relay will drop out when it gets dark and the pump will start again the next day.

There's only one caveat. You may get a pressure surge when the pump starts and you'll need to use a timer to ignore that.

Can you translate pressure in the pipe to an ON/OFF equivalent? In other words, can the water volume itself be the "messenger"?

Can you snake a cable inside the pipe itself, (and thus, not have to dig up or re-route the world)?

-mpm

snipped-for-privacy@cwnet.com wrote in news:1178518058.279436.319380 @e51g2000hsg.googlegroups.com:

A ballcock on the tank and a pressure switch at the pump is what I'd do.

Going all Rube Goldebergish, I'd have the emitter and receiver at the pump end, and use purely optics at the tank to reflect the laser back or not, depending on the level in the tank.

Can you get power at the tank? A small solar cell?

I can get power at the 15000 gallon concrete tank and favor a tip switch firing up a laser aimed at an isolated target pickup at the pump, but have trouble with picking the receiving component . Thanks to all who have responded so far.

The open tank is about 160 feet of lift as well the considerable horizontal distance, so when the 7 foot tall by 20 foot diameter tank is at bottom the pressure is +-80pounds with full tank only

Please see my reply to mpm below. Thank you.

This rings my bell for its' complication alone, perhaps someone could flesh out the hoary details. Yes, unfortunately, there must be details!

Can laser pointers be amped up a tad? Ilike the laser route because it seems easier but still more fun than radio.

Find, or get someone to design, a float valve like a toilet flusher float valve. When the water rises to a certain level, it positively stops the flow (a la your toilet tank).

Your pressure sensor (at the pump end) would be set to cut off at +85 or

Looking up pressure switches is left as an exercise for the reader. ;-)

Good Luck! Rich

Try a search for (laser communicator kit). If you can use a cheap laser pointer to send when water is needed you'll have a ready supply of spares.

You might not need to.

At 1200 feet, you could spot a laser pointer with a spotting scope.

Put a photodector at the focal point of the spotting scope (the "real" image"). Modulate your laser pointer, and demodulate the photodetector signal at the receiving end.

Make sure everything's mounted firmly. :-)

Good Luck! Rich

You can get the Laser part of a Laser pointer without the casing. If you add a really good heatsink and pulse the current in 1uS blasts, you can run them well above the makers intended current rating.

You can buy:

If you apply a current pulse that is short enough, you can bang this with 100mA and it will survive.

Rich, This solution is easily within my ability set and clearly the most sensible way to do the job. However, I'm mostly retired and have the time and basic soldering and electronic tools to go for some form of the laser thing.

What optical receiver would be used as the as possibly the base current for a transistor that would operate a latch relay or such?

It might be as well to add an air vessel on the pump output to provide a holding pressure and absorb any water hammer.