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Counting rotations

Northernlight

New Member
I am an older guy(78) with minimal experience in electronics. I would like to remotely control a fishing downrigger from the boats drivers seat. The downrigger is essentially a winch that lowers and raises a lead ball to which the lure is attached. Luckily the diameter of the drum is such that one full revolution moves the ball 1 foot.
I have no trouble in wiring a remote switch to do this but my problem is knowing how deep it is. I have a 3 diget up/down counter and understand how it works.
My problem is using some kind of simple rotary encoder that will give one pulse to the counter for every revolution and move the counter in the appropriate direction. All I find are ones that give hundred of pulses per revolution. I suspect there is software that is used to sort this out but I’m hoping there is a simpler way.
I did hook up a simple SPDT momentary switch that is struck by a tab on the drum and it worked fine, but it’s noisy and I fear will wear out very quickly.
Any ideas or help would be appreciated.
 

dknguyen

Well-Known Member
Most Helpful Member
Use a magnet on the reel and a hall sensor switch if you just need a tick per revolution. An optical/photo interruptor would work too (either pass through or reflective). Magnetic is more immune to dirtyness.

Search Mouser or Digikey for either and we can tell you if a part is appropriate or not. You may also use the index pulse on any rotary encoder that has one (and pay extra for the hundreds of pulses you will never use).
 
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Diver300

Well-Known Member
A reed switch might be easier to use than a Hall sensor, as the Hall sensor will need power. A reed switch is operated by a magnet, just like a Hall sensor is.

The speed sensor for a bicycle speedometer is usually a Hall sensor, and they come in a housing that might be easier than an un-mounted reed switch.

Do you want separate up and down signals?
 

dknguyen

Well-Known Member
Most Helpful Member
A reed switch might be easier to use than a Hall sensor, as the Hall sensor will need power. A reed switch is operated by a magnet, just like a Hall sensor is.

The speed sensor for a bicycle speedometer is usually a Hall sensor, and they come in a housing that might be easier than an un-mounted reed switch.

Do you want separate up and down signals?
I was not aware of that. Makes sense though. What is the switching frequency of a reed switch? That could come in handy at work.
 

dknguyen

Well-Known Member
Most Helpful Member
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Nigel Goodwin

Super Moderator
Most Helpful Member
I was not aware of that. Makes sense though. What is the switching frequency of a reed switch? That could come in handy at work.
They can often work up to a couple of kilohertz, they are pretty fast devices really. I've got a DIL reed relay here, which I've used for testing various logger/counter type devices, and I stuck a diode across it's coil and feed it directly from a function generator - works great :D

However, they ARE noisy, it's essential to de-bounce them - another reason I was using the reed relay, checking my debouncing.
 

dknguyen

Well-Known Member
Most Helpful Member
They can often work up to a couple of kilohertz, they are pretty fast devices really. I've got a DIL reed relay here, which I've used for testing various logger/counter type devices, and I stuck a diode across it's coil and feed it directly from a function generator - works great :D

However, they ARE noisy, it's essential to de-bounce them - another reason I was using the reed relay, checking my debouncing.
I guess theses are the things that were used in magnetic naval mines right? Maybe antitank mines too?
 

Northernlight

New Member
Thanks guys, I appreciate the comments, but yes, I have to separate the up and down pulses in order for the counter to move up and down. Even if I use two Hall, reed or light sensors, I have to separate the pulse so they both don’t give a signal every revolution, leaving the count the same all the time....one up/one down. I understand sensors and how they work but I can’t find a simple way to use them for this.
Counting the up/ down rotations on a rotating drum must be a pretty common requirement....winches, anchor windlasses, etc.
 

shortbus=

Well-Known Member
Don't think you could build one for the cost of these, look at the whole page not just the featured one - https://www.amazon.com/DIGITEN-Digital-Counter-Proximity-Switch/dp/B016U4IZ6K

But unless you use/have a wheel of a constant diameter that the cable goes over, the length reading won't ever be accurate. As the cable pays out the drum diameter and length per rotation change. But if you feed it over a known diameter say 3.82 inches , it will give you a 12 inch or one foot per rotation no matter what the amount of line left on the drum. There would also need to be a small diameter 'pinch wheel' to keep the measuring wheel turning with the cable so it can't slip.
 
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Pommie

Well-Known Member
Most Helpful Member
A center off spring loaded two way switch will give you up and down signals. Think of a joystick with only the horizontal movement.

Mike.
Note, the above could very occasionally loose counts.
 

Northernlight

New Member
To Diver300: Can you explain a little more as to how this would work....some signal would have to energize the relay before the count begins, then again for the other direction. Perhaps I’m missing something.

Shortbus: Actually, I did order one of those units from China......waited 6 weeks and when I got it, it only worked in one direction. I had to physically move the one output wire from the sensor between the up and down input wires on the counter to get it to work. It had two other wires for powering it. + and -.
Yes, the drum is designed so the outside dia. is such that one foot of cable is moved every complete revolution. The layering on the drum is not really a problem because the cable dia. Is only 1/16” and accuracy is not that critical.

Yeah, Pommie. That works and I have that setup working now but it’s really noisy and I go through a switch every fishing trip. I’m hoping to find something using a Hall sensor or something like that....quiet and non mechanical.

As you can see I have wracked my poor old brain over this problem for some time now.
 

Diver300

Well-Known Member
To Diver300: Can you explain a little more as to how this would work....some signal would have to energize the relay before the count begins, then again for the other direction. Perhaps I’m missing something.
Counting has to be in one direction or another, and when no motor is running, it doesn't matter which direction the counting happens in because there won't be any counts.
You could have a relay that is only energised when the motor is running down. I suspect that the motor is a DC motor, where the power is applied on way to make it reel down and the other way to make it reel up. If so, you can put a diode in series with a relay coil, and put that across the motor.
If a relay is used with NO (normally open) and NC (normally closed) contacts, then the NC contacts are put in series with the up counting, and the NO in series with the down counting.
If your counter has a common connection for both directions, you can use a single reed switch, and a single pole, change-over (CO) relay.
If the motor is DC, and there is a common connection on the counter, the circuit here should work, but as you haven't said much about the counter or the motor, I don't know if that is the case.reel_count_circuit.gif
 

Les Jones

Well-Known Member
Re post #16 There is a potential with that system. If the drum stops with the reed switch closed (Assuming the counter counts on the closing of the reed switch but not on the opening of the reed switch.) going in the clockwise direction and the next movement is in the reverse direction then the counter will NOT change as the reed switch opens so the counter will now be 1 count out. What is needed is for the counter to change on the reed closing in one direction but for the reed opening in the other direction. Many years ago I used that method for a satellite dish position actuator. For that the counting was done on a Z80 micro so the logic was easy to implement. Another way round this problem would be to arrange the magnet system to close the reed switch for about half a revolution and have the counter change on both the closing and the opening of the reed switch. This would then give two counts per revolution so the displayed count would have to be divided by 2.

Les.
 

Northernlight

New Member
Diver300: Excellent idea! I never thought of using the motor’s controls to switch the counters input. I’m sure the motor is a simple permanent magnet type that is reversed by switching the polarity of the 12V power going into it....very simple.
I’m going to try to come up with a relay and circuit that will work and may come back to you with a sketch. I have obligations all day but I will sure be thinking about it.
Thanks again! Very clever.
 

Northernlight

New Member
Les: I thought about what would happen if the drum stopped right on the sensor, also. Apparently only one count is registered on the counter. I have tried it with the switch I have set up. I read that counters read the pulse as the voltage is rising and they are designed with something called “debounce circuitry to avoid that problem...this cheap counter I got from China seems to have it.
 

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