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tkeenan
04-25-2006, 06:39 AM
I am trying to add an automatic shut off to a Hose Reel.· I would like to add a sensor at the point the end of the hose goes into the reel box.· I thought the best idea would be to use a optic sensor of some sort.· Any ideas what might work for this?

Thanks,
Tim

Lee Harker
04-25-2006, 08:28 AM
Tim,
I guess it depends on whether you want to add something to the end of the hose or you want to use a standard hose without modifying it. It seems that a good option would be to have the hose pass through a hole in a bracket of some sort. The bracket could be spring loaded and have a switch behind it. The hose would reach the end and supposedly there'd be a nozzle of some sort that would not pass through the hole. The powered reel would pull with enough force to activate the spring loaded switch and drop out a relay.
How's that sound?

Lee

Eric R
04-25-2006, 11:13 AM
Possibly a shiny metal band at the end of the hose with a IR transmitter and rec at an angle to one another. The reason I say this is that we used to polish one flat of a nut and paint the others black when we built turbocharger based jet engines. Pointing the IR trans and rec at an angle produced a reflection off the one flat allowing us to read RPM. Depending on the reliability of your retract to maintain a reasonable path each time, this may work well for you.

tkeenan
04-25-2006, 05:56 PM
Lee Harker said...
Tim,
I guess it depends on whether you want to add something to the end of the hose or you want to use a standard hose without modifying it. It seems that a good option would be to have the hose pass through a hole in a bracket of some sort. The bracket could be spring loaded and have a switch behind it. The hose would reach the end and supposedly there'd be a nozzle of some sort that would not pass through the hole. The powered reel would pull with enough force to activate the spring loaded switch and drop out a relay.
How's that sound?

Lee
Thanks Lee,

I didn't want to modify the hose.· You have a good idea with a spring loaded switch.· My thought is the reel is moving very fast and stopping that way my cause damaged to the·reel with all the mometum built up.· It seems like I would need to be able to coast a few feet.

Tim

tkeenan
04-25-2006, 05:58 PM
Eric R said...
Possibly a shiny metal band at the end of the hose with a IR transmitter and rec at an angle to one another. The reason I say this is that we used to polish one flat of a nut and paint the others black when we built turbocharger based jet engines. Pointing the IR trans and rec at an angle produced a reflection off the one flat allowing us to read RPM. Depending on the reliability of your retract to maintain a reasonable path each time, this may work well for you.
Thanks Eric,

I think this is also a good idea.· The hose is going though a 2" x 2" hole with rollers on all 4 sides.· I would not be able to point the sensor right at the hose.· How close would this have to be?

Tim

Bruce Bates
04-25-2006, 06:38 PM
Tim -

The "trick" here may be to stop it too early (your "coasting"), and then slam on the "brakes". Depending on what type of motor you're using, this may be easy or may be difficult. The following technique should work for any standard DC motor, any standard AC motor with only one power lead (US 110VAC, UK/AU 220 VAC) and one neutral (earth) lead, but probably will not work with a motor which has multiple power leads (all 3 phase, US 220 VAC, etc).

The sensor, however you choose to implement it, controls a DPDT relay (latching). In its initial state, the relay provides no power to the rewind motor. It also provides another function in this state, but we'll wait on that for the moment. The relay is externally energized, by whatever means is appropriate. It is also latched on, once energized. More about this latching later, if this idea appeals to you, as it's easily done at little or no cost.

Now we're retrieving this hose at full speed, until the "time-to-stop" sensor is detected. This "time-to-stop" point is "n" feet or inches before the nozzle end of the hose. This will have to be determined empirically, and may depend on a number of factors. Suffice to say, there will be an appropriate "safe point" to place the sensed element on the hose body. Once this "time-to-stop" point is sensed, the relay is unlatched and it returns to its initial state. Now, the second function of this initial state is to DEAD SHORT the leads of the motor together. By doing so, the motor will now act as a BRAKE!

Why, you may ask? Inertia is still keeping the motor rotating, so once we remove power from it, it is then acting like a generator, trying to PRODUCE current, and we're going to SHORT OUT these generator leads, causing it to approach an overload condition and work-like-he$$ against the forces of inertia, trying to produce an output which we have directly and purposely shorted. Thus, we come to a "screeching halt" long before we do any damage to the motor windings. Cute huh? http://forums.parallax.com/images/smilies/smile.gif

If you can't "see" the wiring necessary, I'll provide a quick-and-dirty schematic, but don't expect too much. A draftsman I am not!

Regards,

Bruce Bates

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tkeenan
04-26-2006, 08:35 AM
Bruce,

What a beautiful idea you have.· I will have to try and incorperate this braking method.· I am challenged by a sensor for the "Time to stop".· I like the IR transmitter idea but I think you have to be very close to the hose to get a light reflection from it.· The hose is a light green and I thought about painting a black section a couple feet from the end.· Thinking that this would give me a change in the relection.· What do you think?

Thanks very much for the great replys.

Tim

Bruce Bates
04-26-2006, 12:34 PM
Tim -

I was thinking more about your application today, after my last posting. The more I think about this application, I would't use anything but a (say) 12-36 VDC motor. In other words, only low voltage. The first three reasons are SAFETY, SAFETY, and SAFETY!

The last reason has to do with the more robust windings usually found in lower voltage DC motors. During the braking, there may be a good deal of heat to disappate. The more copper there is to do that, the less the chance of burning up the motor. Above and beyond that asset, is that supplying speed control (if needed) will be fairly trivial with a low voltage DC motor. Additionally, there is a pretty decent market for surplus DC motors and gear-motors, from numerous suppliers.

The only downside that I can think of is the need to build or buy a power supply to provide this low voltage DC power, which really isn't much to contend with, for the advantages noted.

Regards,

Bruce Bates

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Grant_O
04-26-2006, 01:02 PM
One high speed optical sensor I have seen, and may be great for this uses ultra-violet / florescent paint, a powerful black light, a photo-diode and a dark-box that the hose passes through. Inside of the dark-box sits the black light that shines on the hose, next to that is a regular photo-diode that doesn’t recognize UV light. If the hose its self doesn't react/floress with the black light then the paint will and the photo diode should detect the bright emissions from the paint!

also i was just wondering these few things to help us better understand your problem...
how do you feed the hose to the spools (is it layed straight out in front of it)?
what is at the end of the hose... is it cut? or are you spooling it to length from bulk?
and how long do you need it to be ~ about?
Is it always going to be the same length?
is it always going to be the same type (size) of hose?
what RPM are you spooling it up at (and we all know as the spool gets larger the hose moves faster)?
so yea, how big do these spools get?
are you using an industrial type machine, or home made

good luck man. hope i helped something

tkeenan
04-26-2006, 06:24 PM
Grant_O said...
One high speed optical sensor I have seen, and may be great for this uses ultra-violet / florescent paint, a powerful black light, a photo-diode and a dark-box that the hose passes through. Inside of the dark-box sits the black light that shines on the hose, next to that is a regular photo-diode that doesn’t recognize UV light. If the hose its self doesn't react/floress with the black light then the paint will and the photo diode should detect the bright emissions from the paint!

also i was just wondering these few things to help us better understand your problem...
how do you feed the hose to the spools (is it layed straight out in front of it)?
what is at the end of the hose... is it cut? or are you spooling it to length from bulk?
and how long do you need it to be ~ about?
Is it always going to be the same length?
is it always going to be the same type (size) of hose?
what RPM are you spooling it up at (and we all know as the spool gets larger the hose moves faster)?
so yea, how big do these spools get?
are you using an industrial type machine, or home made

good luck man. hope i helped something
My spool is an industrial unit I found.· It has a 110 AC motor that moves pretty fast.·
I am spooling a 100 feet of garden hose through a home made hose guide with roller on each side.· This 2x2 inch opening.· I would sometimes pull the entire hose out and other times a few feet.
The spool will be located in the ground and the hose would be feeding from above thought the guides at a slight angle.· As the hose winds on the reel the speed increases.· Hard to say how fast, but a 100' winds up in about 30 seconds.
I like the fluorescent paint idea and the sensor.· I wonder how dark it would have to be.· This reel is located outside and could be in the sun depending on the time of day·used.·· I have never red about this kind of sensor.· Where would you get one?
I appreciate the input and the advise.· This is really a great forum.
Tim