Thanks very much for your input. It's been running at 10 Hz, but unfortunately this makes the room unusable with lights on. Most replacement LED bulbs are very sensitive to line loading (voltage) and flicker like mad. House wiring is all fine, it's just the LED bulbs. I am also in Canada which makes the line voltage drop worse.
I might go for the Crydom SSR in the end, will ponder it over.
Thanks again,
Peter.
Just a quick follow-up that can perhaps help someone else...
I ended-up purchasing a Crydom DC100D40, primarily because I was able to get it quickly and with free shipping, as opposed to the Auber relay that would unfortunately take a while to arrive and was very expensive to ship to my location.
I am now able to run up to 1kHz PWM frequency on the bed heater, although all light flicker disappears just above 100 Hz which is where I keep it. As another HUGE bonus, I am thrilled to have eliminated a potential fire hazard of the stock SSR.
The printer shipped with a DELIXI CDG1-1DD/40A SSR that was installed on two spacer posts with no heat sink of any kind. This SSR was running so hot in use that it was impossible to touch. For kicks, I measured the voltage drop on the SSR when it was on and my jaw dropped even more than the voltage when the multimeter registered 1.65V! This is equivalent to approximately 0.1 Ohm internal resistance, resulting in 27W of power being dissipated by the SSR while driving a 400W load. Unbelievable!
The Crydom DC100D40 under identical conditions measures 0.084 V drop, which is equivalent to just over 0.005 Ohm and 1.4W of power being dissipated. I mounted the Crydom on a small heat sink, per data sheet requirements, which in retrospect was totally unnecessary. The SSR stays cool to touch even under extended full load operation. Beautiful!
@dc42 Thanks for your response.
The board is running Klipper, not RRF, but I know that the setup & configuration is just fine. Note that I am using IO_2 pins 2, 3, 4 & 5 for BL Touch interfacing.
The issue itself is multi-fold and very random in nature: once every few days Klipper randomly fails to establish comms with BL Touch posting "failed to verify sensor state". Several times it also failed to recognize the pin near state during homing, which resulted in a hot end crash (good thing I home with very reduced stepper current). Between these events the printer works fine for days with no issues - including multiple multi-probe 10x10 grid bed geometry measurements with all heaters and steppers on.
It all seems quite random in nature and my prime suspect is EMI & electrical noise due to coupling. I was really shocked to see 0.85V p-p noise on the BL Touch 5V power and SIG lines when the steppers are powered-up, even when not moving. I separated heater & stepper wiring from the signal wiring to reduce any potential coupling. This dropped the noise magnitude to 190 mV p-p. I also switched the BL Touch (v3.1) to 5V mode to improve the noise margin. I don't want to go totally nuts and start using shielded BL touch wiring, so the cap in proximity to BL Touch is meant to be additional "goodness" so that I can start trusting the printer again...
Thank you.
Just a quick follow-up that can perhaps help someone else...
I ended-up purchasing a Crydom DC100D40, primarily because I was able to get it quickly and with free shipping, as opposed to the Auber relay that would unfortunately take a while to arrive and was very expensive to ship to my location.
I am now able to run up to 1kHz PWM frequency on the bed heater, although all light flicker disappears just above 100 Hz which is where I keep it. As another HUGE bonus, I am thrilled to have eliminated a potential fire hazard of the stock SSR.
The printer shipped with a DELIXI CDG1-1DD/40A SSR that was installed on two spacer posts with no heat sink of any kind. This SSR was running so hot in use that it was impossible to touch. For kicks, I measured the voltage drop on the SSR when it was on and my jaw dropped even more than the voltage when the multimeter registered 1.65V! This is equivalent to approximately 0.1 Ohm internal resistance, resulting in 27W of power being dissipated by the SSR while driving a 400W load. Unbelievable!
The Crydom DC100D40 under identical conditions measures 0.084 V drop, which is equivalent to just over 0.005 Ohm and 1.4W of power being dissipated. I mounted the Crydom on a small heat sink, per data sheet requirements, which in retrospect was totally unnecessary. The SSR stays cool to touch even under extended full load operation. Beautiful!
Thank you both very much for your suggestions!
Thanks very much for your input. It's been running at 10 Hz, but unfortunately this makes the room unusable with lights on. Most replacement LED bulbs are very sensitive to line loading (voltage) and flicker like mad. House wiring is all fine, it's just the LED bulbs. I am also in Canada which makes the line voltage drop worse.
I might go for the Crydom SSR in the end, will ponder it over.
Thanks again,
Peter.
Hello,
I am in the process of implementing final touches to my heavily modified CR-10S Pro running on Duet 3 Mini 5+. One of the remaining issues is the bed heater PWM frequency that I would like to increase beyond visual flicker recognition range, effectively above approximately 100 Hz. Based on the empirical results I am seeing, I believe the stock Creality SSR is switching too slow to support this. I was about to purchase a (very expensive) Crydom SSR when I realised that the Mini OUT0 is rated at 18A (TBC).
The printer is equipped with a 400W bed heater that results in approximately 16.7A nominal DC current at 24V. I reviewed the data sheet of the Duet OUT0 LSS MOSFET and it appears to be perfectly capable of handling this level of current. It also looks like the worst case LSS power dissipation would not be substantially above ~1W. One marginal issue could be the 15A fuse that might trip when exposed to 16.7A for prolonged amount of time.
Does Duet3D have any long term use experience with this magnitude of DC current? The fuse, if it's an issue, could potentially be stepped up to 20A but I would then have concerns with the integrity of board traces under fault conditions. I am not concerned with the thermals as I have a well designed forced cooling of the board back side and I also use one of the ADC inputs for thermistor based board temperature monitoring. Currently the component side PCB temperature between the most heavily loaded stepper drivers (X&Y) never exceeds 55C.
Thank you,
Peter.
Thank you for the explanation @dc42.
Hello,
Ever since I acquired the Mini 5+ I was wondering why there are only four 100uF VS filter capacitors for the five TMC drivers. The schematic confirms that Driver 0 does not have the 100uF low ESR capacitor that the remaining drivers 1 through 4 have.
Thank you.
Quick update: after many prints and countless hours of me trying to purposefully trigger BL Touch misbehaviour, I can confirm that everything has been working perfectly.
In the end I did four separate things:
@dc42 Thanks very much for your suggestion! The Klipper config does indeed use '^' to enable the internal pull-up and describes how the pull-up is required by BL Touch. But of course only for boards that do not provide external pull-up! This also explains why the 'voltage low' level was reading unusually high in my installation (I cannot remember the exact value but it was around 1V I believe. Combine that with .8V noise and just over 3V for 'voltage high' and there was really not much wiggle room left!
I now disabled the internal pull-up and reverted the BL Touch to default factory setting. I will keep my eye on it for the next few weeks.
Thanks again for your help!
@dc42 Thanks for your response.
The board is running Klipper, not RRF, but I know that the setup & configuration is just fine. Note that I am using IO_2 pins 2, 3, 4 & 5 for BL Touch interfacing.
The issue itself is multi-fold and very random in nature: once every few days Klipper randomly fails to establish comms with BL Touch posting "failed to verify sensor state". Several times it also failed to recognize the pin near state during homing, which resulted in a hot end crash (good thing I home with very reduced stepper current). Between these events the printer works fine for days with no issues - including multiple multi-probe 10x10 grid bed geometry measurements with all heaters and steppers on.
It all seems quite random in nature and my prime suspect is EMI & electrical noise due to coupling. I was really shocked to see 0.85V p-p noise on the BL Touch 5V power and SIG lines when the steppers are powered-up, even when not moving. I separated heater & stepper wiring from the signal wiring to reduce any potential coupling. This dropped the noise magnitude to 190 mV p-p. I also switched the BL Touch (v3.1) to 5V mode to improve the noise margin. I don't want to go totally nuts and start using shielded BL touch wiring, so the cap in proximity to BL Touch is meant to be additional "goodness" so that I can start trusting the printer again...
Thank you.
Good day,
I have another off-the-beaten-path question regarding the Mini 5+. I am currently troubleshooting an occasional random BL Touch behaviour. In my installation the BL Touch is wired using approximately 1.5 meter length of 26 AWG conductors. I have done a lot of work using an oscilloscope to minimize the electrical noise and coupling that the Bl Touch sees - it used to be 0.85V p-p and now it's below 190mV p-p.
I would like to also add a low-ish impedance Nichicon PW power supply decoupling capacitor in the proximity of the BL Touch. What would be a sensible maximum capacitance that the Mini 5+ can tolerate on its 5V internal regulator? I tried with a 33uF capacitor and everything is working perfectly but I would like to go a it higher, if possible.
Thank you,
Peter.