Magnetic Reed Switch with Counter and Electric Solenoid - Help Required

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mark31a

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Hi folks,
First time posting and new area for me - I’m a mechanical engineer!
I’m looking to build and electronic circuit for an old farm bale wrapper I am refurbishing.

Im going to fit a magnetic reed switch to the spinning bed to count the revolutions. I want to set up a circuit, so when the reed switch counts up 30 revolutions of the bed (maybe displayed on an LCD) it sends a 12v signal to an electric solenoid on the hydraulic supply and stops the rotation of the wrapper, then a reset button for the next bale.

The whole aim is so someone dosent have to stand counting the wraps on every bale!

Would be interested to hear your thoughts!

Cheers, Mark
 
Welcome to ETO!
Many years ago I made a bale-wrap counter but found that the constant uni-directional motion of the magnet past the reed switch eventually magnetised the reed so that the switch stayed permanently closed. You will therefore need to be lucky/careful in your choice of reed switch. I also found out the hard way that all wiring has to be kept well out of the way of farm animals. Cows liked to use the machinery as a scratching post!
My counting circuit was made with 74xx series TTL logic ICs and the display was 7-segment LED units. Nowadays an MCU would be a more suitable choice. I daresay there are off-the-shelf counter/display modules available too.
 
Hi Mark

Welcome to ETO .. .. .. .

Being a Philistine, I'm not sure what a bale wrapper actually is, but the project sounds like an ideal job for a small Arduino processor and a Reflective Sensor like a HOA 1405. With no moving parts and an accurate count each time, probably a pound seats job. I like the sound of the challenge.

There are folk on here with much more experience than me, who will probably advocate using something more sophisticated like a PIC micro but for us novices that is much more difficult to achieve and I don't think the sophistication is needed.

I'd be glad to help if I can.

Do you have a picture of your bale wrapper ?

MM
 
alec_t said:
found that the constant uni-directional motion of the magnet past the reed switch eventually magnetised the reed so that the switch stayed permanently closed.
Click to expand...
Use two magnets, 180 degrees apart on the wheel, one rotated with respect to the other. Count to 60.

ak
 
Not only dust. Hot/cold/wet weather and animal excrement aren't very good for optics/electronics either .
 
There are industrial counter modules on ebay that have a preset function and relay output. IIRC $20 ish.

ak
 
What is the nature or physical appearance of the spinning bed? This may affect the decision on what is the best sensor.
There are better options that reed switches.
I know you mentioned that you are a mechanical Engineer but the Pic micro (8pin) would probably do the trick with ease, Do you really need the LCD display?
Either way, you could use a Mosfet to switch the relay and remember to use a BEMF diode across the relay coil.
Max.
 
If small magnet used, there are also small Honeywell SS400 devices unipolar, bipolar, latching etc.
Max.
 
Without knowing the exact details of the mechanics, I would assume you do not want to place the sensor out in the open or the periphery of any large rotary item.
If so, it may be worth looking to incorporate the sensor at the centre of rotation where there is a likelihood that there is a cover or other means of protecting the sensor.
Max.
 
You can get off-the-shelf batch counters of various types, that will trigger an output when a preset value is reached.

A couple of examples - the first one even includes a proximity switch to trigger it:

6 Digital Counter With Proximity Switch Sensor NPN Electronic Length Batch Meter for sale online | eBay

Find many great new & used options and get the best deals for 6 Digital Counter With Proximity Switch Sensor NPN Electronic Length Batch Meter at the best online prices at eBay! Free delivery for many products!
www.ebay.co.uk

87629113 | Crouzet CTR48E Digital Counter, 6 Digit, 115 V ac | RS

uk.rs-online.com
 
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