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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 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 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 19:31

hey Stan,thanks. I am new to this too 🙂

– Voltage, yeah. this can get tricky. In this case it seemed more reliable to explicitly set the Arduino’s Voltage reference. At the moment it’s powered by the VFD via 24 -> 5 transformer. Possibly I should try 12 V again.
– Hall vs Rotary encoder : trust me, you want them both just. The hall sensors needs exorbitant wiring; something I can’t leave existing users alone with. The rotary encoder is doing pretty well btw., it’s accurate and enables you fast and precise reactions. For now I have still to wait for recommendations for a good hall sensor. Also, the speed sensor needs no extras, just plug it directly (it wants 6+ V).
– Temp. sensor, sorry. It wasn’t in the picture but the Max6675 controller seems to hold up great; no false alarm since days. It’s the same thermocouple we use for anything else too.
– Housing:  yes, it’s just a box with plugs for sensors, speaker and VFD signal cables. In the bazar version with VFD included it will be open on the side since there is cooling provided from the VFD (all in one big enclosure). For the stand-alone – v3 upgrade version; yes, might be better to close this entirely; amazing to see where and how folks run their shredders 🙂

Anyway, still have to check all PCB options and from what I see til now the whole thing can be just 1/5 $$ & time wise of this very DIY version (which we keep maintaining).

thanks again,

29/08/2019 at 19:57

Why isn’t the hall sensor as simple as something like this and a small magnet? https://www.banggood.com/Hall-Effect-Magnetic-Sensor-Module-DC-5V-For-Arduino-p-76469.html . Plugs directly into arduino with 3 wires at 5V.

29/08/2019 at 20:14

@s2019 : I haven’t used it til now and preferred to wait for more details on this approach. From what I understood it’s measuring amps and looking at the wiring (do I need special glasses to read it ?, see more project page) there are quite some more steps to do (including tuning, also code tuning to make it more effective). I would consider this being complicated and somehow dangerous for existing users with no prior background.. The speed sensor on the other side just needs the magnet with 4 inducting stand-offs to work; and from what I saw til now; it just works – you can bid your cat on it. The hall sensor is great as backup and over-torque protection. Also, for now I consider this a nice experiment which turned out successful – now it’s time to get this boxed – rather not so funny after all, except you’re watching enough cat videos on the side 🙂

07/09/2019 at 16:03

status :
– custom PCB idea ditched for Arduino compatible DIN rail PLC
– draft design for complete shredder & extrusion controller done
– SSRs, power supply and other components going to be replaced for DIN rail version
– extrusion : i will try a multi-channel PID with external controller, ie: touch-panel (profiles & settings)

bitter pill : such industrial controller, subject for certification will add 400-1000 Euro to the material bill.

features : auto-reverse (hall & rotary encoder), over – torque & heat motor protection, along with additional breakers (for folks who keep trying in case of  failures), hopper & enclosure open – sensor, metering (energy alarm and/or profiles ? )

next : investigate certification, the enclosure is already IP – 65

see you in a bit

18/09/2019 at 07:55

Haha, i found your github code before I found this forum post.


I’ve tried your code but there’s a few differences between the systems, so i’ll have to dig a bit into the code or just ask here when i get stuck.


Im using a single phase motor connected to two contactors (one for reverse, one for forward, Schneider part number LC1D09M7).  The contactors are activated via a two channel omron SSR (photo is shared with this post), so one output pin from arduino for forward and another output pin for reverse.  Easy enough.


I got confused with hall sensors as there’s some that work as proximity sensors and others work as current detection.  Mine is the proximity type and costs less than 0.5euro.  its the same that @s2019 was asking about, you can google ky-003 to find it.  With no magnetic field present, sensor wire outputs high, with magnetic field sensor outputs low, it does not put out an analog value.

Now i’m just a little confused over some of the wiring with this code, like the 3 way switch.  I simply want “up” to be forward, middle to be off, and “down” to be reverse.


The values for turning the relays on and off were inverted for me which i just now discovered, now i feel like an idiot.  Anyways, i’ll make another post once i sort it out.


The code is great, i really like the configuration and it makes sense without much explaining. Kudos for that!

Here’s some photos of the hardware I’m using, also an Arduino nano because why not?  I do regret using it as it uses a usb mini cable which is going the way of the dinosaur.

18/09/2019 at 11:19

@bulegila, yeah. The hall sensor might get a little complicated. I am adding support for  another one today : ‘LM393’ – optical sensor – which is capable to measure  up to 700RPM. I consider this one to more easy and reliable over all the others; only problem is that you need a disc with at least 15 holes – but easy too.

I am updating the wiring diagram this night, hang on. For the contactors : I ordered those and try my best this week but as long they are accepting a low-voltage – it’s no different than controlling the VFD – over a relay. The 3 pos switch pins btw. are wired internally in the opposite direction.

I am setting up a new discord – server – ‘PP Help & Support’, and some extra channels as ‘culture’ , ‘live’ and ‘eletronics’. Last time I asked for such channels – we’ve got banned, lol.

18/09/2019 at 16:27

Ah, i dont understand why you’d get banned for things like that, im sure admins have their reasons, maybe something else?

OK, i had a bad toggle switch so that explains quite a bit.

I’m only having trouble with the proximity sensor side of things, maybe you can help? In the serial monitor it shows all switch positions beautifully.  Sensor value just keeps increasing on its own regardless of what the sensor is doing. Even if i simulate movement with a magnet and my proximity sensor, the system is indicating that its jammed and will run two unjamming cycles (reverse, forward, reverse, forward, halt). I’ve changed the input mode from input_pullup to just input and it has no effect.  I have continuity from sensor wire to arduino pin.

Please tell me I’m missing something and you know exactly what it is. 🙂

18/09/2019 at 16:49

– I guess it’s the normal sensor, with a blue, black, brown wire
– I hope you disabled everything else for now (IR, TEMPERATURE, HALL, STATUS)
– Just to make sure, the proximity sensor is setup like this (https://www.instagram.com/p/B1lpYs0DVj8/)
– I hope you wired it like this (https://precious-plastic.org/home/library/components/shredder-auto-reverse/) , more or less

I’ve setup a dedicated discord server for support and extra-terrestrial visitors like myself , here the invite : https://discord.gg/tYnb99h (I will be there 8pm, berlin time)

18/09/2019 at 19:36

– forum bug

19/09/2019 at 15:18

changes :

– support for IR sensor as rotary encoder added: works pretty good now (check wiki for CAD files) and I consider this the more easy and stable. one more open challenge is to package the encoder disc and the sensor into an easy to mount addon for v3, v3.1 and v4

– reset button better integrated with status lights
– added support for disable/enable auto-reverse button
– code adjustments after long run tests

20/09/2019 at 21:19

getting there, usability and fault tests unveiled a few surprises but other than that, green light for using the IR sensor.

Since this baby is the first micro electronic controller driven product & also the first open source addon (or standalone) on the Bazar, we think it deserves a name : the ‘HAL 9000‘ (youtube video) ! Not to be confused with the HAL 9000 HD which can’t be deactivated at all, only tossing it in space may help 🙂

next updates for the IR sensor mount coming next Tuesday. Still waiting for v4 details to get this roundish for all PP versions …

In the picture below you also see :
– safety tests for cat tails and rotating couplings = all ok, nothing happened
– humble use of orange, we heard that orange is too seducing for some folks
– ‘project zoe’ – our best seller – soon going fully open source as well – after 10 months in production there are amazing details to be shared

23/09/2019 at 18:07

Here some shredding tests as video (320 Nm). Pleasure to use, you just keep filling the hopper. Now I am just amazed how patient people must be to work without auto-reverse. With a little more tuning this should speed up things even more. time to update the performance tables of v3 and I am so glad that some folks can use the shredder for basket play, for real 🙂

26/09/2019 at 19:21

new changes after using this device for some days :

– added a config variable (IGNORE_FIRST_DIRECTION) to prevent sudden shredding (and possible bad surprises) after power up
– some disco like flashing on the status LED bank during auto-reverse

next :

– extra button to set it to extrusion only mode (no move = fatal)
– interfacing a second circuit / micro controller – to dial in better and faster extrusion parameters or profiles (we need your data !) – this will take a while  since I have to hook up a touchscreen (also for 3d PET print and/or extrusion as automatic injection,..) on a RPI yet.

fun stuff – hacking PP as nobody is watching but from what I’ve seen, it’s pleasant and feels way more safe as before 🙂

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