Author: Woody

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Simple Water Level Sensor for Live Steam Locos

Avoid a panic half way round the track

While coming to the end of a running session of my 5″ loco at the club raised level track I suddenly realised the axle pump was not making its normal rattling noise. Water level was likely very low and there appeared very little in the glass sight gauge. My state of panic endured until I reached the filler hose.

On returning home to the workshop I resolved to try to make this alarm situation more readily visible. The common solution is to add a second sight glass feeding from the water tank and visible in the ‘cab’. My engine did not have a great deal of room for this addition.

Sacrilegiously I began to consider an electronic solution which probably wouldn’t make me popular with the mechanical diehards but the challenge appealed.

The electronic solution turned out to be a multi faceted activity. An initial bird’s nest lash up was followed by a PCB designed in Fusion 360 Electrical. The PCB was milled on my vacuum table fitted to the Tormach 440 with the Gerber and Epsilon files converted to GCode using FlatCAM. Having completed the PCB board this led to a customised enclosure designed in Fusion 360 and 3D printed in the Qidi X Smart 3.

The circuit is a NPN transistor that is turned on by water conduction between two sensor probes which in turn drives a second NPN to illuminate a flashing LED. The module is powered by a CR2025 button cell.

The enclosure consists of three parts, the base, a snap on lid and a round boss that matches the diameter of the water filling hole on the engine side tank. The two water sensing probes are made from 16 swg wire protruding from the boss.

The round boss is held in place with a M2.5 countersink screw and could be dimensioned to suit different sized filler holes. Having it as a separately printed item is also useful in that it allows the enclosure base to be 3D printed without support.

Here is are some views of the completed assembly.

It seems to work quite well and is surprising sensitive down to the last few millimetres of the probe rods. Time will tell.

If you want more details then please send me a message.

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Dry lining wall fastener fixing aid

Simple jig that makes DIY easier

In my experience there is only one fixing style that works with plasterboard lined walls. These are shown in the image below and are supplied in various mounting thread sizes. The image below shows the 4mm and 5mm versions. Also shown is an example of how they expand out when you clamp them inside the cavity behind the plasterboard. Note that while intended for dry lined walls, these can also be used on thin walled surface such as a modern ‘hollow’ door (good for bathroom towel hooks). The fasteners are available in various lengths to suit the mounting surface thickness.

In use you drill the appropriate clearance hole for the body (6.8mm for the 4mm version and 8.8mm for the 5mm version) and push the fastener into the hole so it is flush with the outer surface of the plasterboard. You tighten the screw to cause the ‘wings’ to expand in the cavity.

There are a few issues with this. To cause the expansion process to start you have to apply a lot of pressure downwards on the screw head. Once you feel the screw beginning to turn easier you are on the way to crushing the wings against the wall inside surface. The next test is judging when you have reached optimum expansion of the wings. This comes with experience. The screw rotation will go from relatively easy to increased pressure.

When used on plasterboard the two triangular prongs on the fastener are supposed to grab into the plasterboard surface and stop the fastener rotating as you tighten the screw to initiate the wing expansion. My experience is that you need to apply heavy downward pressure on the screw head to stop the prongs just rotating free and cutting a nice circular vee groove in the plasterboard surface. This is slightly less likely to happen if you are fitting one to a hardboard surface such as a hollow door as the hardboard will give greater resistance to the rotation.

This tightening process can be helped if you put a washer under the screw head with some grease. This eases the possibility of the whole fixing rotating.

You can buy a tool for mounting these fixings. My version is a 3D printed double pronged restraining jig. So far I have created two sizes, one for 4mm and one for 5mm threads. It is simply a disc with two 1.6mm panel pins embedded in it that mate with the notches in the fitting. The tool is offered up over the fastener with the pins in the V grooves and then pushed home into the plasterboard. The pins embed deeper in the wall surface than the prongs on the fastener and stop it rotating.

A couple of other comments. Once you have the fastening in place on the wall the screw thread will likely be longer than you will need to hold the object being fastened to the wall. You can therefore substitute a shorter screw as needed so long as it is long enough to mate with the fastener thread. You can also change the screw head style. When fitting curtain battens I use a number of these fittings along the batten length and replace the dome head screws with countersink heads into which I fix the commercially available small plastic star head covers (see below).

Here is an image of the fasteners, the two jigs sizes I use, a view from the rear of how a fastener expands in the cavity and the small coloured plastic covers that can be used to cover countersink screws.

Depending on the technique that has been used to fix the plasterboard, you can sometimes have a reduced depth of cavity for the fixing. This can be overcome by drilling the mounting hole for the fastening not just through the plasterboard but as deep as need to match the fixing’s length into the solid wall behind. This allows you to get the fastener in place and the expansion of the wings will not be inhibited. Clearly this is not so easy with a steel lintel behind the plasterboard …..

The STL files for the two sizes can be downloaded on the link below. I used PLA with a 4 perimeter print and 0.25mm layer depth. Once printed, clean out the two panel pin mounting holes with a 1.6mm drill. Cut the panel pins to around 6-8mm length and push home into the drilled holes. The small counterbore on the print surface will match the fastener flange but not to full depth so there is a pressure exerted from the jig as you push it against the wall.

cavity-fastener-jigsDownload

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Simple Vice tommy bar modification

Protection from getting trapped skin

I have a Record #34 vice. It has a seriously chunky tommy bar. If you accidently let this drop with a finger in the way you are heading for expletives and a large blood blister.

The fix is to force two O rings over the end stops to act as buffer protection. Apart from lowering your blood pressure and saving your stock of BandAids it reduces the clunk when the bar drops with or without your skin in the way.

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Arduino Giga Display Shield and lvgl.h

Should Arduino be called Harduino ?

When the Arduino Giga appeared on the market with its associated glossy Display Shield it looked like a programmers dream.

I am not a programmer. Sitting down to do a software project to me is like writing off a large lump of my remaining MTBF.

John, my close friend in France, is an also ran in this respect. We both fumble around doing cut, paste and edit development and end up with some quasi stable code that might do the job intended.

So joy of joys the Giga appeared and John got excited … which rapidly degenerated into acute frustration, hair pulling and suicide by software tendencies.

I got sucked in to help – blind leading the blind.

I tried running all the Arduino demos for the Giga Display Shield and after an inordinate length of my life had passed I concluded that any sketch with ‘#Include lvgl.h’ in it would be unlikely to run.

Slight digression. What is not made generally clear is that with lvgl library you have to edit the lv_conf_template.h file and re-save it in the Libraries folder as lv_conf.h. The edit is simply to change a 0 to a 1 and instructions are in the text at the top of the file listing. This edit enables lvgl. I spotted this and duly did as directed. Still no joy.

Out of desperation I deleted the lvgl library version 9.0.0 and replaced it with the 8.3.11 version. I then had to do the 0 to 1 and do the Save As etc routine again….

To my huge surprise this worked . See below as a simplistic overview of the changes needed.

So progress has been made and there are some nice demos to watch now that they are running OK. Note that the Arduino IDE will constantly tell you there is a later version of the lgvl library but you have to ignore this and opt for manual update. If 9.0.0 does get loaded you will have to go through the above process again to the extent of removing 9.0.0 and replacing with 8.3.11 but the edited lv_conf.h file will be unaffected so you don’t have to repeat the edit and Save As process … hopefully someone will fix it in the near future.

I would further add that not all the published demo sketches work. If you want a reliable sketch to demonstrate the camera onto the Giga screen download from Kurt’s depository on the link below.

https://github.com/KurtE/Arduino_GIGA-stuff/blob/main/sketches/GigaCameraDisplay/GigaCameraDisplay.ino

Conclusion – maybe metal bashing, Fusion 360 and 3D printing suddenly have a much more attractive appeal.

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Qidi X Smart 3 revised fan installation

This is the final offering … well, for the time being ….

I have been slowly evolving my ideas for fume filtering when using the Qidi X-Smart 3 printer. I should say there is nothing majorly wrong with the fan system as shipped but there always seems to be background residual fumes even when printing PLA. The level of fumes does seem to be dependent on the brand of PLA used.

The rear fan as shipped has no HEPA filtering, it simply vents the chamber into the external air. This fan only comes on during the printing process.

I have previously posted some early ideas for improving this using readily available HEPA filters. Following some discussion with Christian, a fellow X Smart user, we worked together to evolve this further.

The first phase was to upgrade my external fan filter duct design to have both HEPA and a carbon granule filter sections. The carbon granules are sandwiched between two 10 gauge stainless steel meshes and an outer cover holds everything in place.

The result of this looked promising but the axial fan as shipped lacked a decent air flow through the filter stack. This was upgraded to a 6028 centrifugal fan mounted on an adapter plate. The Fusion 360 assembly is shown below.

Below is a simplified cross section view. The internal fan adapter plate flange and the external filter stack are bolted together through the back wall of the printer using the original fan mounting holes and M3 screws and nuts. The fan is mounted on the adapter plate using M4 screws and nuts. There are moulded nut cavities to make assembly easier. The cover plate which holds the two meshes and carbon granules in place uses M3 screws into 3D modelled threads in the corner holes.

As previously posted I had fitted a full size Bento filter to my Qidi ifast. Further discussion with Christian revealed he had fitted the Bento Mini to his X Smart and seemed impressed by the internal air scrubbing action. I looked at the design of the Mini and after some thought changed the carbon cavity filtering walls from a printed grid to using the same 10 gauge stainless steel mesh as used above. The Bento Mini printed well and I was impressed by the thought that had been put into the design. There is a version with a hanging bracket designed for the X Smart 3.

I now had a belt and braces solution – the Bento for internal scrubbing and the HEPA/Carbon filter pod on the rear extract fan. Here are some images of all the components in place and the small terminal strip to interconnect the 24V supply.

The fans used on both assemblies are the same dual bearing 6028 models as detailed in the Bento write up. These are rated at 24V @ 80mA. The axial fan originally fitted was rated at 130mA. I removed the original fan and wired the Bento and the extract fan in parallel and connected this to the original supply feed from the control board via a small terminal strip. The two fans are only commanded ON during printing.

That is my hopefully my last solution but as ever it will depend on actual performance to see whether I notice the difference in air quality. Mission creep is always possible.

As mentioned in a previous post, I designed some booster feet to fit over the existing feet on the printer. These increase the air gap below the printer to allow more air flow. If you print them in TPU they gave extra stability to the printer and reduce resonances.

Here is a link to the STL files and write ups for the simple duct, the fan adapter plate, the two stage filter duct, booster foot and also the modified Bento carbon box and lid with mesh divider walls. Note of late I have been printing with a setting of four perimeters which gives stronger modelled threads.

Thanks again to Christian in Germany who has been a great help in bringing these various mods to fruition.

X_Smart_compendiumDownload

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