Strain PCB Effector faulty?
I'm just writing this thread to inquire what someone might have to offer in the way of resolution to an interesting problem i just came across yesterday. I had, about a week ago, received two parcels. One containing one compete smart pcb effector setup (including haydn's arms, pt100 sensor, 24V heater cartridge, pcb components), and the other containing 2 additional basic kits only (just pcb components and heatsink).
So, I assembled and have had excellent results with the first of the two packages (the entire system), and have been getting better results than ever before with my delta printer. Then yesterday, I decided to assemble one of my additional effectors to host a volcano hotend version and realized once it was all together that while everything functioned, the strain sensor was not working. I figured maybe I was too rough with it during assembly and that maybe I scratched the surface or something. Then, I opened the second extra effector from the second parcel containing the two additional ones I bought, and this time was extra careful not to mishandle the board during assembly, but to my dismay, the second of the two additional boards I received displays the same defect: everything functions except the Z-probing strain function. Just to be sure it isn't the wiring on my printer, I reattached the original assembly which had been functioning just wonderfully and voila, working just fine.
It seems like both pcb effectors that came from the second package are both defective, and I'm having difficulty believing that could be possible. Please advise.
Oh yeah, thought I'd mention for completeness sake that upon powering up the printer, both boards flash twice the LED that indicates contact, but other than those two initial flashes, I can't make the LED illuminate again thereafter, no matter if I tap or flex the board…nothing. In contrast, the working board initializes with the same two flashes, but thereafter, any touch of the board (even the slightest brush against it) causes the LED to light up in response. That's how it should work, I know that.
It does seem strange that 2 boards would be faulty, but as you have the third one working i can't think of another explanation right now. Please email info at Duet3D dot com to discuss replacements.
Thank you David for your prompt reply…and I must say, what a fantastic solution to the delta issues I had previously been up against. I say this as in currently printing with the one working pcb effector of the bunch and it is just astounding how well it's working for me, I must say. Though, I'm not able to currently obtain results like others have of variances after a G32 of next to nil, such as 0.007 like some users, but I am getting the best numbers I've been able to obtain yet with any other solution of approximately 0.031 (which is technically sufficiently low to work well, and he proof is in the results, which for me is finally having reasonably great looking output!! Thanks so much.
If it's any consolation, I'm not getting deviation down to tiny levels either. Probing 16 points at up to 150mm radius, I get around 0.024mm.
Funny enough, yes, that does actually make me feel a bit better off. I wish there was some way to figure out what could be stopping these two pcbs from providing the strain function…because otherwise they're perfect...lights go on a as soon as my thermostatic control hotend fan realizes hotend is above 60C, etc...just not giving me touch feedback which is a bummer cuz u dare not tinker with the one that works, but I desperately want to try the volcano high flow nozzle with my new printing abilities (compliments of your cool new effector release!). Any ideas on what to look for?
The second photo at https://www.duet3d.com/DuetAddons/DeltaSmartEffector shows the underside of the effector. The components near the top edge handle the strain gauge, so you can check that no components have fallen off.
If you have a multimeter, you can check the resistance of the strain gauge elements (with the 8-way connector not connected). There are two resistors labelled R13 and R14. The right hand ends of them are connected together, and the strain gauge elements are connected between the left hand ends. The total strain gauge resistance should be in the range 60 to 100 ohms. The junction of the two strain gauge elements is connected to the right hand end of R11, so the resistance between there and the left hand end of each of R13 and R14 should be around 40 ohms.
Be careful not to let your multimeter probes slip and damage the strain gauge traces, especially if they the probes are sharp, because the warranty does not cover mechanical damage caused by the user.
On second thought…maybe I just should leave it be and you can have a look upon receipt of it back to you. While I'm confident in my abilities with regards to utilizing my multimeter properly, I don't see really any possibility except for problems by opening up the possibility of it being a user damaged issue while it's currently DEFINITELY NOT that. Probably better that you pros have a look at it when it arrives back to you so you can determine how it could be that the two from the same package were DOA while the other works perfectly. It is interesting to know though, for future reference, what values ought to be displayed by the components.
Thanks anyway, and looking forward to the working replacements as I've finally been able to print satisfactorily every since assembling that first board which worked and has been working brilliantly. I can't say enough about what a great development this device you've come up with has been for my experience. Literally changed the game for me.
Yes, I think that would be the best thing to do.