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Help needed, electronics – shredder auto-reverse

This topic contains 45 replies, has 10 voices, and was last updated by  Anonymous 6 months ago.


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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29/08/2019 at 18:11

I’m an arduino/electronics novice but here are some thoughts:
I thought powering the arduino with 5V, other than through the USB is tricky https://forum.arduino.cc/index.php?topic=271158.0 .
I’m not sure I would trust the header/jumper connections. You could use a Nano and mount it in a screw base https://www.banggood.com/NANO-IO-Shield-Expansion-Board-For-Arduino-p-963967.html . Or maybe just solder to the arduino and have the relay module provide the screw connections.
I wonder if for the overtemp you could use a simple thermostat module. Set the temperature and relay opens once it is reached something equivalent to this https://www.banggood.com/Geekcreit-W3230-DC-12V-AC110V-220V-20A-LED-Digital-Temperature-Controller-Thermostat-Thermometer-Temperature-Control-Switch-Sensor-Meter-p-1416355.html .
For cooling, you are just pushing signals through the box right? So maybe just some vent holes, or maybe not even that, keep things dirt resistant.
The two line LCD’s are pretty cheap but if you use a thermostat which displays temperature, then the rest could be status LED’s.
For the speed sensor, you could switch to one of the small cheap hall sensors that may be easier to find room for.
My understanding is that getting a low volume run through one of the Chinese PCB prototype shops is pretty cheap once you have a design.

29/08/2019 at 13:13

Ok, going the long way getting this one done a little more appealing and viable I checked youtube and it unveils making PCBs with a cheap CNC isn’t that hard.

One can order the PCB with the provided plans soon. That leaves us with this tasks open :

1. design different enclosures – for all sensors (proximity as rotary encoder, temp. sensor for motor over heat and the hall sensor). That could be a simple one from the hardware store (annoying to do), a 3D print variant (about 1 day print) and a variant using CNC cutted acrylic plates (sandwich style) using hex standoffs and metal meshes for the sides which I like most since the cooler from the inverter can be shared within the same enclosure.

2. design the PCB and find all mentioned components again, for such design (Gerbel ?)
3. find an Arduino compatible micro-controller (recommendations ?)
4. develop single phase variant (just bigger relays)

No idea where the price is then but I hope it’s getting below 100E in the bazar. Needless to say having a good auto-reverse and other protections seems urgent to me. We had recently even a customer blowing up an extrusion motor – which I considered impossible. So this baby should rule them all.

thanks everybody  🙂

29/08/2019 at 13:04

— forum bug — sorry for the double post

29/08/2019 at 00:28

I so i tried to wire the first unit for a customer. I spend around 50 Euro til now and wiring took already 4 hours – not even finish (possibly another 3). From a business perspective this design doesn’t make much sense. I would have to charge 200 – 300 Euro for all (cooling, plugs and good cords for sensors, CNC cut enclosure – small as possible!) and it still feels like a toy. I don’t trust much those connections and an Arduino with screwshield would be in the 50 – 80 Euro range. On a 3D printer those connections seem alright though 🙂

Any ideas how to speed this up ? A custom PCB with screw sockets and a custom Arduino would be lovely.

27/08/2019 at 16:53

this story turns out to be quite some fun 🙂

Change log :
– added optional inputs : hall sensor as done by @dirkvanvroeger as well a sensor for measuring the motor temperature. so you can use them all together. just activate them in the configuration file.
– added optional output : alarm sound. I am adding a bright alarm LED (which one ?) to signalize shredder failure so you can see that from far as well.
– updated documentation for a 24 V transformer version to supply everything with the  24V from the inverter.

open challenges
– proper wiring (screw shields ?)
– good enclosure (cooling?)
– interfacing for the settings, I am intending to set the settings via Bluetooth and the upcoming pp mobile app. There are LCD with touch keys shields but I am running out of input terminals and going for Arduino Mega is a little much except you want a little interface to enter shredded plastic/type, etc… and then read & upload via app the data …. I don’t mind; it’s fun 🙂

26/08/2019 at 14:10

Hi folks,
The documentation & Source Code for alpha version has been uploaded here.

@dirkvanvroeger would be great to have this linked as alternative in your project.

Next iteration for more features comes mid of Sept.
– LCD for settings
– Temperator sensor for overheating
– Hall sensor for over torque
– Eventually logging/metering

22/08/2019 at 19:20

Just for anyone interested, I made some more tests with the proximity sensor. Here some notes:
1. cheap, those sensors are 5 bucks just and what’s left to get is a 4 channel relay bank to control the inverter (forward/stop/reverse) and perhaps a 12 Volt supply (those sensors need 6V+ but that’s often provided by inverters already)
2. stupid easy; all you need to do is measuring the delta times between sensor on/off and if it exceeds some thresholds, then you activate forward/reverse logic just as in the v4 hall sensor approach.
3. would work also for single phase but needs bigger relays

Now I’d just have to build the mount and housing for the sensor compatible to the v3 side plates. The last thing to solve : possibly a magnet holding a wheel with at least 4 inducting metal points (screws, pins,…) as seen in the picture flipping the sensor signal. The sensor it self reacts in the 4mm range so it doesn’t need calibration. This would work with extrusions and v3/v4 shredders, single or 3phase; doesn’t matter. Anyway, fun stuff; There is just a little headache how to make this as commercial unit (water, existing wiring, manuals, …).

Updates soon here again with project page and code 🙂

24/07/2019 at 15:57

@deeemm, thanks i just saw it; At the end the more reliable way of measuring the running RPM is a proximity sensor and 2 magnets. I gave up on inverter feedback as it won’t apply for VFD less setups anyways. I tried the amp sensor of Mr. Kegel but I couldn’t apply this either to different setups and audiences.

case closed for me, thanks again 🙂

03/07/2019 at 09:30

@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

20/06/2019 at 20:38

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 🙂

19/06/2019 at 19:29

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.

19/06/2019 at 19:07

@s2019, thanks a million; exactly what i wanted !

19/06/2019 at 16:58

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).

19/06/2019 at 16:33

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 :

THEN REVERSE(4Secs) ; FORWARD() // uses 4YwRobot relay

code comes this weekend

19/06/2019 at 10:03

@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 😉

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