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Help needed, electronics – shredder auto-reverse

This topic contains 22 replies, has 5 voices, and was last updated by  Mick Percy 2 days ago.

1
Create Sense pex12

Help needed, electronics – shredder auto-reverse

18/06/2019 at 20:34

hey there, as part of a v3.1 update we’d like to finish the ‘auto-reverse’ function. for now it works only with 3-phase inverters in ~120 Euro range since they have an error signal when stalled or over-torque occurred.

I’ve made it all ad-hoc so all control switches (direction, speed, emergency switch, 5 quick speed-dials) can be used without the add-on.

however, I get a little stomach pain thinking to ship this unit to countries with 40+ degrees Celsius, high humidity and dust.

Anyone has a recommendation for a solid Arduino based unit as well a 5V relay bank ? I was even thinking to integrate a Raspberry-PI with touch-screen for metering/monitoring but I have little trust in this stuff when it comes warranty or run-time for 2-3+ years. The entire unit is stupid simple and currently below 10$; All it needs are 100 lines of Arduino code and some good enclosure. I’d also prefer a complete analog solution but my skills on that is too little to make a good PCB.

For single phase motors, I can’t recall the name of the sensor but i guess any optical encoder like sensor will do; i am just worried about high – power relays …

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dedicated
19/06/2019 at 10:03
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@sensibill, i think it’s your terrain; eventually you have a recommendation for a long lasting arduino based unit given the mentioned conditions above. eventually i am just pessimistic but most of this cheap stuff doesn’t last long in my hands 😉
g

starter
19/06/2019 at 16:10
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If you get an OEM Arduino, they are pretty rugged and if you don’t need too many IOs it’s fine, and if they do fail its $10 and low voltage

I haven’t done any switching like this with an Arduino. Not to say it couldn’t be done.  you would need something like a 5v coil relay like an Omron g2r-1-s ( 5v is on the lower end of their range but they are reliable) with the contacts getting the power from a 240V-24V power supply. The 24v relay contacts then switch a 240V contactor like this. That’s basic levels that you might approach it, with the Arduino getting the speed information from the motor fan or the drive shaft to detect a jam/over torque situation.

I was going to do the same as you have done with the Arduino communication with the inverter. I managed to pick up a used delta one still waiting for it to arrive. It would be good to see your Arduino code.

dedicated
19/06/2019 at 16:33
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great, thanks a lot; i will check it out this night, after work 😉 i am even considering to set a bounty on it to make it full analog but I guess keeping the unit simple to plug and disposable and easy-to-replace will do in the short term.
i am finishing the code over weekend but at the end it’s simple :

AUTO-REVERSE – LOOP :
IF OVER-TORQUE && !EMERGENCY && FORWARD (5V)
THEN REVERSE(4Secs) ; FORWARD() // uses 4YwRobot relay

code comes this weekend

dedicated
19/06/2019 at 16:58
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evtl. it’s better to introduce also 1 more states : RETRY_TIMES (how often it tried) to make sure it’s not trying to shred the same obstacle (metal pieces) all over again; needs a little more extras : LED (unshreddable).

warrior
19/06/2019 at 18:48
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I have not used these and they cost more but may be an option.
https://www.rugged-circuits.com/

dedicated
19/06/2019 at 19:07
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@s2019, thanks a million; exactly what i wanted !

warrior
19/06/2019 at 19:22
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Also found this with CE certification.
https://www.emoro.eu/shop/index.php?route=product/product&product_id=52

dedicated
19/06/2019 at 19:29
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nice, so that means the controller can go fully assembled out on the market; stand-alone with optional power supply (inverter provide this too). so what’s needed is to plug the inverter or only the motor (inverter incl.) ; neat, i love it.

dedicated
20/06/2019 at 20:38
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ok, i ordered all that stuff; @sensibill, a link to your inverter ? the solution is pretty generic as i see now; possibly i can make it work for your unit as well. i will head over to single phase. @s2019, thanks again; i went for ‘rugged’ for now but the ‘EMoRo 2560’ is darn good; evtl. this can be used controlling a auto-plunger and also metering. metering deserves an own topic; it was always tempting to build a unit which measures drawn amps per shredded kilogram but at the end this would be quite a downer to see what happens actually behind the scenes 🙂

starter
21/06/2019 at 07:40
1

@pex12, I managed to pick up a used delta inverter (VFD075M43A), I picked up a 4kw 3PH WEG motor still in its crate for the last few years, so got lucky with that.

Both of those boards have some nice extra features and definitely can take more abuse, nice find @s2019.

warrior
21/06/2019 at 16:26
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On the rugged circuits site there is a great read https://www.rugged-circuits.com/10-ways-to-destroy-an-arduino . I think I’ll start a checklist for myself.

starter
02/07/2019 at 12:12
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Hello,It is not clear to me,
how to connect Arduino kit (5v)
To the connectors (220v)
currently used to manually turn a single-phase motor?
best regards
itamar.

dedicated
02/07/2019 at 14:30
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hey there; sorry, with the heat wave and other things i hadn’t much time to progress on this.

@itamar : this post is currently only looking at 3phase motors using an inverter (around 100 Euro) which gives you all the inputs/outputs as parameters to dial in suited acceleration and declaration. even though; you still need relays to toggle the inverter control flows (around 20 V) for direction, stop and speed. in the case of single phase motors you have to use 220V relays which also can deal with the high currents (near 8 – 20+ Amps) which turn off/on the flow of a single phase line. as you don’t have an inverter which gives you an error signal, you have to build an encoder (old printers have quite some optical sensors; combine this by cutting out a gear like disc from plastic or carton) to detect your motor is still turning the shaft. with that you can use the same code as for a 3phase setup. i hope this helps.

starter
03/07/2019 at 09:13
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Definitely important details!Thanks.Did you mean such a relay? …

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dedicated
03/07/2019 at 09:30
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@itamar, that could do too; in this case please harvest some old CPU coolers or get some from amazon (ssr cooler); those relays  don’t last very long. i never tried this on a shredder motor; not sure what’s the peak amperage draw for start; usually you need a start capacitor in this case but also a run capacitor. single phase isn’t exactly a good choice for efficient high – torque applications. In case of doubt, please ask the fine folks at the PP – Electronic – Department

dedicated
04/07/2019 at 10:38
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@itamar, here is a picture of the encoder; be aware it needs a slightly more complicated algorithm if you use only one optical sensor. i think there ready to use boards for lathe spindle encoders which use at least 2 sensors; check the CNC forums.

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starter
05/07/2019 at 17:02
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Hi,I build the inversion system with arduino  Relay sensor.
Hoping to succeed.

warrior
05/07/2019 at 19:09
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@itamar , Interesting, post your schematic and sketch when you have it.
Thanks

dedicated
05/07/2019 at 19:17
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yeah, I would be interested too. Regarding stall/overtorque signal: after testing my variant against a few inverters I am now switching to an optical encoder too. I couldn’t get a clean signal out of them all, despite I’ve done my best sorting Arduino analogue-reference issues though. Makes the hole thing more generic; a one-for-all solution 🙂

helper
06/07/2019 at 19:13
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I used a simple ACS 712 – 20A Sensor on one of the three phases. The output is really unsmooth, however if you use the following code, all the AC-disturbance will be smoothed out.

 

http://henrysbench.capnfatz.com/henrys-bench/arduino-current-measurements/acs712-arduino-ac-current-tutorial/

Thats how far I got. You can easily see the zero-load consumption of the shredder and the peaks if it shreds material or thicker parts.
After that you need to program a algorithm which calculates the average over time to smooth out the current-peaks. Then you can set a limit and you are ready to go.

 

One more thing is that the current reading over time might change as the motor coils heat up and the resistance/current changes. This might be compensated by an additional temperature sensor at the motor. Like a db18b20 sensor.

An optical sensor might help as well to eliminate this uncertainty. I thought its easier to solve things within the electric cabinet, rather than to add mechanical sensors.

starter
07/07/2019 at 01:13
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With these components … a drawing will follow …

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dedicated
07/07/2019 at 10:48
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thanks all; @friedrich, i will try it out. At the end I’d like to have a complete ready-to go controller (with enclosure) for shredder and extrusion; So yes, if it can be done without a sensor but also without adjusting code (POTs are ok) then fine with me.

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