Help needed, electronics – shredder auto-reverse
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 …
@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 😉
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.
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
@s2019, thanks a million; exactly what i wanted !
Also found this with CE certification.
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 🙂
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.
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?
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.
Definitely important details!Thanks.Did you mean such a relay? …
@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
Hi,I build the inversion system with arduino Relay sensor.
Hoping to succeed.
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 🙂
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.
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.
With these components … a drawing will follow …
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.
Most inverters have programmable outputs. You can use this with simple relays to create automatic reverse function. There should be the possibility to trigger an output at a defined torque or current level. You can use this to monitor if the motor has stalled.
Here is how to make it work…
Program inverter output to switch at defined torque or current level.
When activated this output activates a relayThe relay latches itself and swaps the fwd / rev control signal to the inverter which reverses the direction of the motorThe relay also also activates a second relay, the second relay is a delay-on timer relay.After a pre-defined time (eg 5 seconds) the second relay activates cancelling the latch on the first relay,The first relay de-energises allowing inverter to run forwards again.
The inverter normally has several different control profiles eg how fwd / rev / run are connected. You need to choose the profile where applying a fwd signal causes inverter to run forwards and applying a rev signal causes inverter to run backwards, and removal of the signal causes it to stop. If your inverter does not have this kind of profile and requires an additional run / enable signal you will need to provide additional wiring to activate this. This may require additional an relay.
Most inverters have limited on board low voltage power supplies (24v), which means that they will most likely not create enough power to be able to drive the relays, so an external PSU may be required.
I’ve attached a simple schematic of the wiring.
@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 🙂
Ahh cool, the post is fixed 🙂
Just noticed that the N/C contact on the first line is unmarked, it should be T1
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 🙂
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
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.
– 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 🙂
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.
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