Treth, how steady are your G31 readings if you repeatedly issue them in quick succession? I always see a spread of up to 7 counts.by Radian - Ormerod
@KimBrown - I do like the look of your dark red glass, although it's not for the squeamish! I wonder if my other half would mind me raiding her stained glass making supplies!!! Probably not worth the risk. @Treth - I understand what you mean about waiting before publishing. If you do get round to it though, I hope you put some photos in your topic.by Radian - Ormerod
QuoteGregL Feed the lightly tinned wires into the ferrule - feed a little more solder into the open end And I should have added that if solder does flow around the outside it's easy to clean off by applying your iron for a few seconds and wiping over the molten solder with a stainless steel pan scourer (these make magnificent soldering iron tip cleaners too - much better for the iron than wet spby Radian - Ormerod
Hi Kim, Interesting that you set the Z probe reference point to just 0.1mm above the bed... is this to reduce the ambient coming in from the sides? I suppose if the probe can be used to shadow itself it could help. If that's the case would it help to form a jacket around it?by Radian - Ormerod
Quoteepninety ...or the energy available at switch off... Dave Rest assured - there's precious little of that! From what I've seen with the Alpine PSU, even with both heaters off, the reservoir caps barely hold up for a missing mains cycle. With the bed heater on, it's down within a millisecond or two. I've not looked at the PS_ON# response but it's almost certainly equivalent to disconnecting tby Radian - Ormerod
Good progress all round then :-) I do like this method of Z probing, mine's never been so reliable! Oddly I haven't found it being discussed for this particular application anywhere else, yet it seems ideal, and none too expensive. I bought-in some more Ultrasound devices today including transceivers (optimized for both TX & RX) and some 25kHz modules - advantage: bigger window of height toby Radian - Ormerod
Quotebalidey Thanks all for replies, glad its not just mine that don't fit. The crimps were done by a professional electrician with decent crimp tool, it left it as a pretty tight square, but still nowhere near going to pass into the terminal. I will make sure I regularly check screws. Dave, you say its NOT a good idea to tin wires, but the instructions specifically say TO tin them, to stop theby Radian - Ormerod
Thanks for the heads-up! I'm wondering how freely your filament comes off the spool though... what kind of reel support do you use?by Radian - Ormerod
Hi Dave, I'm pretty sure it's not an injected noise artifact as the readings remain constant when I dismount the sensor board from the X carriage and run the Z motor. However, I can just about half imagine how the offset might come about given that the wave isn't simply standing still with the sensor at a fixed point within the wave, but the sensor is moving towards the reflection. However, I'mby Radian - Ormerod
I've still not discovered the reason for the fixed offset. All I know is that it's highly repeatable so, for the time being, I work around it by adding whatever offset I get after homing following setting the probe point with G31 Z4 Pxxx, i.e. by following up with G31 Z4.4 Pxxx so that all subsequent homing takes it all the way down to zero. However, IMO the overall scheme seems like a definiteby Radian - Ormerod
Sorry, forgot to mention about temp.co's... the idea is to always home at a set temperature. As you pointed out, Z homing is best done when the bed is at working temperature and with the head just above the bed it seems likely to be pretty consistent. OK, its not as tight as a reference oven but I think it's much better controlled than the ambient IR issue. I still worry that the real limiting fby Radian - Ormerod
I made a table of values vs. height but it's no longer valid after reducing the time constant of the peak hold. It now has 100K/1uF. Roughly though, the reading is at an all-time minimum (say 500) at zero height, then climbs to an all-time maximum (say 650) at around 3mm. However, the Z home routine always starts above this, certainly above 4mm - so by taking a reading at 4mm, where the level isby Radian - Ormerod
Update: Built (bodged) a prototype on a scrap of stripboard that fits in exactly the same place as the original. The PIC12F1822 simply drives the transmitter using its PWM output as per the drawing above. The peak held output provides a very similar level to the original - i.e. at a few mm above the bed, G31 gives around 600. (The 5-way socket on the bottom edge is for a ISP lead) The transby Radian - Ormerod
I don't understand that; most transducers seem to be around 2.5nF. JIC I didn't describe it too well, here's a diagram of the cct I used to get a DC analogue value of the distance: In this circuit I'm decoupling the transducer from the driver using a 3K9 resistor so it's driven on both half cycles unlike the idea I had before to decouple on the -ve half cycle. That gave a greater voltage swingby Radian - Ormerod
I now realise that I don't understand the orientation of your board Anyway, there are tons of SM LEDs around - some are sideways-firing for edge lighting etc. I doubt you'll get a good light throw from anything else, but it may be the only way.by Radian - Ormerod
The diode is a neat way of "loosening" up the response but it all depends on how we want to sample the results. Right now I'm trying to make q drop-in replacement for testing, and all it consists of is a SO8 PIC (could be a 555) to generate the 40kHz and then a peak holding diode/cap directly off the transducer driven by 3K9 from the PIC. Unlike like the original IR setup, this analogue level hunby Radian - Ormerod
Quotedc42 It's looking as though there will only be room to fit two 5mm LEDs for illumination, using Matt's one-piece fan/heatsink design. 5mm LEDs as in LEDs with leads? These are usually narrow-angle - I think it needs as wide an angle as possible which means SM, and the combined forward volt-drop of three LEDs and a 390R @12V is very practical. Maybe some like these perhaps?by Radian - Ormerod
There's a very simple way to "see" more of the interference and that's to let the transducer freewheel for half a cycle. This is easily done by driving the transducer from a GPIO pin directly via a diode. The diode blocks the negative cycle so a resistor is needed across the transducer to damp the energy but that's all there is to it. video of it in action on Vimeo The green trace is the 40kHby Radian - Ormerod
Might be worth a try, you can get magnetic sheet (A4 inkjet printable for example) that could replace the heat spreader. Not sure how it would stand up to being heated though.by Radian - Ormerod
The ones in the cans look ideal for mucky printing beds - but are a bit heavy on price! have the best selection I've seen. The prices have gone up a bit since I last played with ultrasound though. Do you think it would be better to select a source with as narrow a beam angles as possible? If we want to create the maximum amount of constructive/destructive interference it seems logical to focus aby Radian - Ormerod
Quotedc42 I just did a quick test on an ancient ultrasonic transducer I had lying around. The greatest difference in amplitude I was able to see between the first maximum and first minimum was about 10%. So I think this method may be feasible. However, the maximum and minimum are not sharp peaks, so it may be better to calibrate at the point halfway between. Right, but what sort of source impedaby Radian - Ormerod
Quotedc42 Instead of measuring the phase, which would require 2 transducers, I think it may be possible to rely on the fact that at 2mm or so range, the standing wave between the bed and the transducer will affect the impedance of the transducer, and hence the amplitude and phase of the signal across it when it is driven from a high impedance source. So we could look for a maximum or minimum in tby Radian - Ormerod
Mike, I accidentally hit the post rather than preview and went back in to edit in pretty much what you just said! The ambient temperature is a pretty big factor and it has to be taken into account, yet it might even benefit from the closed-loop bed heating already in place. The air temperature near the bed surface might be even more predictable for a given set-point than it would be without activby Radian - Ormerod
Hi Mike, from Wikipedia Ambient Temperature can be compensated for in software as it has a known relation to velocity of sound. Temperature can be inferred from bed thermistor and or a local sensor. Shouldn't be too much of a problem.by Radian - Ormerod
Quotedc42 Radian, I will be hand-populating the boards with SMD parts and solder paste, then reflow-soldering them. I mostly use 0603 components. In that case maybe your next project should be Pick and Place RepRap styleby Radian - Ormerod
I keep thinking about Z height too. If I understand the scheme you describe, the nozzle will be in contact with the bed so it relies on a perfectly clean nozzle. Also, the fully automatic bed compensation routine will have to raise and lower the head in each corner unlike any non-contact scheme. So far I've ruled out capacitive sensing, inductive sensing, force sensing... not so keen on IR, whicby Radian - Ormerod
dc42 has done sterling work with the IR sensing and continues to explore other solutions. I have another proposal which I think ought to have it's own topic to avoid any hijacking! A 40kHZ Ultrasonic source and receiver can measure time-of-flight to and from the bed to within a few millimeters, and switch to phase comparison for final homing below 8mm (25us/cycle * 340um/us = 8500um or 8.5 milliby Radian - Ormerod
dc42, have you thought about supplying it as a kit? I'm used to hand assembly of SM parts and I'm sure other people would be too - so long as you don't go lower than 0805 and 0.05" - and you mention doing the assembly yourself by hand anyway. Just a thought as I've been here myself and even fulfilling small orders in the dozens gets to be a real PITA in no time flat. By kitting it in addition toby Radian - Ormerod
No worries Treth - I was just looking for confirmation that the supplied part was identical to the ones other people here had obtained. IMO the original nut is an insanely close fit on the threaded rod which, while good for backlash, obviously has a serious wear issue. I have a great deal more confidence using the nut you found. Thanks for the heads-upby Radian - Ormerod
I ordered some JDY01.M05 as well but they're a bit sloppy on the original Z rod. With the original steel nut I couldn't measure any backlash at all but there's around 0.2mm with the new nut. This is measuring at the tip of the rod that hasn't been worn. Anyone else notice this?by Radian - Ormerod