I have one module with drivers specifically for the 'standard' steppers and a different module designed for the X27 type motors.

.

I think we'd all be interested in seeing what the driver you use with the X27's is, as I know that I am not alone in seeing jittery movement with them

Cheers

Les

 

I think we'd all be interested in seeing what the driver you use with the X27's is, as I know that I am not alone in seeing jittery movement with them

 

Cheers

 

Les

My mini stepper module uses the AX1201728SG driver.

Thanks - I presume that the drivers were soldered to a breakout board, which I have tried without success to do. However your feedback does encourage me to keep trying, as it sounds like it is a good potential solution. Any tips on getting them to work? I was pretty careful to attach them to (purchased) surface mount adapter boards, but must have done something wrong! Do you have pictures of the PCB so that I can see if it the same type I have tried?

Cheers

Les

Thanks - I presume that the drivers were soldered to a breakout board, which I have tried without success to do. However your feedback does encourage me to keep trying, as it sounds like it is a good potential solution. Any tips on getting them to work? I was pretty careful to attach them to (purchased) surface mount adapter boards, but must have done something wrong! Do you have pictures of the PCB so that I can see if it the same type I have tried?

 

Cheers

 

Les

I didn't use a breakout board to mount the drivers. I have a custom designed PCB that includes the driver chip, microprocessor and all support circuitry. The microprocessor manages the interface between the driver chip and my I/O system software. It has custom firmware that handles the acceleration/deceleration, homing, and other special features for driving the motor. As far as the connection of the driver chip, I just followed the guidelines in the spec sheet for the driver. I don't recall any special 'Aha moment' in the design of the driver circuit.

My PCB is soldered in a reflow oven so the parts are not hand soldered. If I were going to hand solder the driver chips, I would look at a schmart board for the breakout board. The schmart boards are specially designed to make hand soldering easier. During development, I had quite a few failures which I think indicates the chips are very sensitive to handling and hand soldering. Also, during development, I had a high rate of dead on arrival chips ordering from various vendors on AliExpress.

I am reliably producing my mini-stepper modules so take heart that it is possible to make it work with these drivers.

I/O System Improvements

I've got most of the instruments complete and decided it was time for an update to my I/O system so I could start working on some of the other panels. I needed to add the ability to read switches and to drive LEDs. I also wanted to expand it to allow connections to additional flight sim programs.

My software is designed with a main portion that does all the common tasks like configuring your cockpit and calibrating your gauges. Then it uses plug-ins to handle the different interfaces to the flight sim programs. I wrote new plug-ins so now the system supports IL-2 Sturmovik Cliffs of Dover, DCS World (WWII planes), X-Plane, Prepar3D and FSX.

To tackle switch inputs and LED outputs, I looked around and found there were reasonably priced hardware options already available so rather than design my own hardware (like I did with the stepper modules) I decided to write an interface in my software to support an external hardware device. I chose to support the PoKeys57 from PoLabs. This device has 55 I/O points and is quite flexible in how they can be configured. They can be configured as digital inputs, digital outputs, analog inputs or encoder inputs (and maybe some other stuff that escapes me at the moment). For now, I only support digital inputs and outputs, but I can see other options coming later.

With the I/O system updated I'm now in a position to start making switch panels...

 

 

My PCB is soldered in a reflow oven so the parts are not hand soldered. If I were going to hand solder the driver chips, I would look at a schmart board for the breakout board. The schmart boards are specially designed to make hand soldering easier. During development, I had quite a few failures which I think indicates the chips are very sensitive to handling and hand soldering. Also, during development, I had a high rate of dead on arrival chips ordering from various vendors on AliExpress.

 

I used the commercially available SOP/SSOP to DIP Adapter boards for this, which worked well with other SMD chips, but whether it's a combination of poor soldering techniques (I have no access to a reflow oven) or poor quality chips (I have no way of testing them prior to fitting to the boards) is not clear.

I have some new chips coming from a seller in Germany, so will have another go with those when they arrive

**** EDIT ****

As it happens they must have arrived yesterday, they were in the post box this morning. I mounted one of the chips on the adapter board, and I'm pleased to say that it worked perfectly using the schematic and sketch here https://guy.carpenter.id.au/gaugette/2017/04/29/switecx25-quad-driver-tests/

So, all I can assume is that the previous chips I had bought were DOA (from two different sources) so will have to be wary of that going forward. All I have to do now is splice in the code for the AX1201728SG drivers into one of the gauge sketches and then repeat the tests I did to see if it makes any difference to the quality of the movement. I hope so, after all the trial and error!

Cheers

Les

 

Finally, no matter how smooth your gauge movement is, the actual smoothness of the indicator will be limited by the update rate of the data. For example, if the sim outputs engine RPM at 2 times per second your gauge will see big jumps in the commanded position when you rapidly increase the throttle. If the RPM data is output at 60 times per second, the incremental differences in the commanded position are smaller and less noticeable as individual steps. So you will be affected by the rate at which the data comes out of the sim and the rate at which it is then forwarded to the stepper driver.

I did a test today, using four X27-0168 steppers, each driven by an Arduino Nano via (respectively) an EasyDriver board, an A4988 driver board, the AX1201728SG driver and finally directly driven by the Nano. All were set with the DCS BIOS sketch for the APU temperature so that I could see how they performed with the different drivers at the same time. The result showed them all acting almost exactly alike, crucially including the jitters. At low pointer speed, they all virtually simultaneously stepped from one position to another, stopped together then stepped again. The steps were large relative to what the stepper motors are capable of.

As a result, I am now sure that the pointer movement quality is (as you say) driven by the output from DCS BIOS. Even the addition of a smoothing algorithm made no difference at the lower speed due to the slow position refresh rate.

So I will have to change tack on all my work to improve it.

Les

Switch Panels: The basics

This is a pretty long tale for such a basic topic and in fact, it took quite a bit of calendar time to get through all this. Anyway, here's my saga.

In order to start making switch panels, I needed to figure out how to make them. I already know how to wire up switches to an I/O system, but I mean something much more basic than that. How can I create the panel itself and make it meet my overall goal of balance between looking like the real thing but not costing too much?

I'm building a warbird pit, so these panels are different than the ones most of us are familiar with for the newer jets. The newer ones are thicker and backlit. The ones for the warbird are essentially a piece of aluminum with cut-outs for the switches and silk screened text/graphics. Sounds pretty easy, but my problem was the text and graphics. Most of the text is about 1/8” tall (3 mm). Then there are graphics which are mostly lines and arrows. I can print plastic panels, or cut out panels in plastic or thin aluminum using my CNC, but how to apply the text and graphics? (By the way, this is the same problem I encountered very early on in making my gauges: How to make the face plates? It's a large part of the reason I decided to buy old aircraft gauges and adapt them.)

I experimented with engraving on my CNC, but I wasn't able to get the small text to look good. Most likely not an equipment problem buy my inability to make it do what I wanted. (This might become a recurring theme.) Either the letters didn't engrave cleanly, or the depth of engraving wasn't consistent enough. I tried engraving in that two-colored plastic they use for trophies but the top black layer is too thick. It doesn't look right because when you v-carve the letters have to be too big. If you don't v-carve, you can't see the white letters unless you look straight on to the panel. I tried painting a panel white, then black, then engraving through the black. I couldn't keep the depth consistent enough and again the shape of the letters wasn't reliably good enough.

Next I was on to the 3D printer. I tried 3D printing a panel with the text already “engraved”. Similar results to the CNC: in order to make the letters look good they had to be too big. It also left me with the problem of how to “paint” the letters white – by hand? Yikes no.

Next stop: labels. I could buy custom labels. I've used them for other things and they stick pretty good to aluminum. I could make a blank panel, then apply a custom label to the top of it that contained all the text and graphics. The problem here was the finish of the labels doesn't look too much like the real thing and the custom labels are a bit more expensive than I wanted.

Researching turned up some not too expensive silk screen equipment. Of course I thought “hey, I'm pretty handy, I can do that”. Well, apparently not. Much like the CNC issues, I suspect it's an operator error problem more than an equipment problem but I was unable to get my custom silk screens to sufficient detail that I was happy with it. I even called some local places to see if they would silk screen the blank panels for me using my custom designs – no takers.

Finally I came around to stencils. The idea was to make a blank aluminum panel, paint it black, then apply a stencil and spray paint the white text/graphics. Sounds simple enough (surely I can use a spray paint can, but by now my confidence was shaken), but how to make custom stencils for lettering that is only 1/8” high? I tried a laser attachment for my 3D printer to cut out stencils from label material. Similar problem to the CNC: getting the cut detailed and consistent enough was tricky. One letter burned to wide, the very next letter didn't burn all the way through.

I started looking at automated stencil cutters. This seems to break my rule of not spending too much, but it is in keeping with my rule that each new project gives me the right to purchase a new power tool, and to be honest, I was getting desperate by this time. The biggest problem was that I couldn't find a stencil cutter that advertised it could do text as small as 1/8”. Searching the internet it seemed to indicate this wasn't something people generally tried to do with these cutters. I finally found two blog entries where someone had done something similar using a Silhouette brand cutter. The cutter wasn't a complete budget breaker and was well reviewed. So after taking about a week to convince myself to spend the money just to try it, I pulled the trigger and ordered one. After one or two attempts, I managed to get the quality I was after.

So now my process is:

1. Design the blank panel and cut it out of 1 mm aluminum sheet on the CNC.
   
2. Spray paint the panel black.
   
3. Design the stencil and cut it out on the Silhouette cutter. Larger panels have the stencil broken into smaller sections that are easier to handle.
   
4. 'Weed out' the stencil. This means using a pointy thing to pick out all the bits of stencil material from where the letters have but cut. (The stencil cutter cuts the outline of the letters, then you weed out the center piece, leaving a letter-shaped hole in the stencil material.)
   
5. Carefully align and apply the stencil to the black panel. Use painters tape to mask any remaining areas of the panel.
   
6. Spray paint the panel white and remove the stencil.
   

In the end, the panels look pretty good and are pretty inexpensive. The aluminum sheet is not to expensive and neither is the stencil material. So if I ignore how much I spent on the cutter (refer to my rule about a new power tool on each project) I met my goals of looking good without too much expense. (I know it's a stretch, but like I said, I was getting desperate.) After all this time researching and experimenting, I was finally ready to actually make a panel...

Right Switch Panel

The right switch panel has a number of different features so I thought it would be a good one for this post. I'm working on the rest of the switch panels, but most of the techniques I will use there are shown here.

Panel

I made the bare panel as I described in the previous post. The only thing I'm learning is that the 0.04 inch (1mm) thick aluminum sheet is perhaps a bit too thin. It flexes a bit. I think I can live with it for the panels I've already built, but I am going to try some slightly thicker sheet for the next one.

Ammeter

The ammeter gauge was built just like all the earlier gauges I've posted. In this case, I ended up only reusing the housing, face plate and pointer. I replaced the rest of the internals with an X27 type stepper motor and a 3D-printed back plate with a connector in it. The only thing special was that I had to open up the stepper and glue in place a new stop. Normally they run about 350 degrees but for this offset pointer, that was too much. As you can see in the picture, this swings less than 180 degrees.

Lights Dimming Switch

Nothing to see her folks, just move along.   I don't use the dimming switch so this is just a dummy potentiometer, panel mounted, and using a knob I found on Amazon that looks similar to the original.

Triangle Switch Labels

I 3D-printed the triangular “labels” for the switch labels. They are aluminum in the real plane, but I didn't feel confident in bending up aluminum pieces, including the screw holes in the top crease. After a bunch of sanding, filling primer, and paint, they were smooth enough to stencil in the same way I did the panel.

Switches

The two DISC switches and the two HEAT switches are aircraft equipment. The current ratings don't match the aircraft but since I just hook them to the I/O, that doesn't matter. The remaining five switches (the shinier ones) are commercial replacements. Just standard toggle switches that are about the right size and have the correct 3-position function. They don't mount like the aircraft switches, so I 3D-printed some mounting adapters for them. If you look closely on the rear picture, you can see them.

Circuit Breaker Cover

The circuit breaker cover is a 3D-printed cover, attached to a plastic hinge I bought and modified. Like the triangular switch labels, the cover required sanding and filler/primer to make it look smooth (like the aluminum piece in the real aircraft).  Behind the panel I installed some aircraft circuit breakers (not exactly the right type for the aircraft). The breakers aren't functional (they aren't simulated in DCS anyway). I used similar mounting adapters to the ones I made for the switches, since the breakers I chose didn't mount the same way as the aircraft.

Multi-position Rotary Switches

There are multiple special rotary switches in the P-51 cockpit, as there are in all aircraft cockpits. These are the rotary switches that have multiple positions, with varying amounts of rotation between switches. I needed a way to implement these, but I didn't want to spend the expense of buying the mil-spec parts. Even if I did, some of them couldn't be found. (Maybe because the P-51 is so old.) So I decided to allow a little artistic license in my simulator on this point. I decided it's acceptable for the switch positions to be similar to the aircraft but don't have to be perfectly matched. For example if an aircraft switch had positions as 33 and 52 degrees rotation, I would accept a switch with positions at 30 and 60 degrees rotation.

Having given myself some latitude in the area of accurate simulation of switch positions, I came up with the idea to get standard multi-position rotary switches and modify them to meet the needs of the individual switches I needed to simulate. I decided on a 12-position rotary switch because it gave a pretty good resolution of 30 degrees per switch position. That seemed like a pretty flexible starting point. (Nothing I needed required anything less than 30 degrees per position anyway.)

The idea is to start with a 12 position rotary switch (with positions at 30 degree intervals) and a stop that keeps it from rotating past 330 degrees. Next, disable any positions I didn't need. For example if I only needed positions at 0 and 60 degrees, I would disable the detent at the 30-degree position and don't wire that position into the I/O. Then, put a new stop after the 60 degree position. Now I would have a switch that has two positions with detents at 0 and 60 degrees.

I started with a basic switch available from several online vendors, the key was to look closely at the pictures to see if it looked like the switch could be disassembled for modification. I found this one.

Here it is disassembled.

The only thing not meant to be pulled apart is the snap ring that holds the detent mechanism together. The snap ring is made from soft (cheap) metal so it deforms. I have been able to reform it for reassembly twice, but I guess it will fail if I try a third time. So the thought is just don't rework a switch more than once or twice. (Get it right the first time.)

Here we can see how the detent mechanism works and how I modified it.

The piece on the left is made of something like a spring steel and rotates up against the piece on the right. The little balls are pressed into place against the piece on the right. The piece on the right has raised bits around it's circumference. When the balls fall (or are pressed) into one of the gaps, you get a detent. There is another raised bit in the piece on the right, just inside the detents. That's the stop. The piece on the left has a raised area next to one of the balls that contacts the one on the other piece preventing it from rotating any further.

With this knowledge in hand, the modifications were pretty basic. Fill in the detents I don't want and make an additional raised area in the piece on the right where I want the new stop. Looking closely at the piece on the right, you will see I've filled in the detents I didn't want with epoxy. Look even more closely and you will see where I've used a punch from the other side to make a dent from the other side. It's pretty small, but that's all it took to make it act as a stop.

Reassemble the switch and Bob's your uncle.

The only thing that was a little tricky was keeping track of which positions I wanted to fill in and where the new stop should be to get the configuration I wanted.

This is my solution  for a custom 5-way, 360 degrees rotating switch.

It's basically a PCB with 5 microswitches arranged in a circle.  As the handle is turned, a disc with a bump on the bottom presses one of the 5 switches.
In the bottom section is a pentagon that turns with the shaft and a sprung arm that acts on the flats of the pentagon to make a 5-position detent mechanism.

4 hours ago, No1sonuk said:

This is my solution  for a custom 5-way, 360 degrees rotating switch...

That's an inventive solution.  The lever arms on the switches seem a bit directional.  Have you had any issues with turning the switch "against the grain" where the bump approaches the switch lever from the higher end?  (In your picture above, that would mean rotating the switch clockwise.)

That looks like the P-51 fuel selector.  Are you building a Mustang simpit?

It IS the P-51 fuel selector
I'm not building a simpit per se.  I'm building some bits and pieces to make flying a bit easier, in some cases, I'm making those bits like the real ones for the challenge.
e.g. my fuel panel:

I've made combined fuel gauges, and added low level warning lights.

WRT the switch levers:
The model is a bit simpler than the real ones, which have bent over ends.  I've not noticed any difference in which way the lever is turned.



Here are some of my P-51 threads with the bits I've made so far:
 

P51 Aileron Trim Test Piece:

MS25041-STYLE Press to test indicator (P-51 landing gear lights):

P-51 Mockpit Build (Mostly just the fuel selector and gauges):

Nice work!

A New Shell

A while back, I got a new fiberglass shell for my cockpit. Here it is with a fresh coat of paint and some grip tape covering the floor.

And now with the instrument panel and throttle installed.

Now I'm remaking all the cables to fit the routing in the new shell, then I'll start transferring the instruments into the new shell.

Reconnecting the Throttle Quadrant

I finished reconnecting the throttle quadrant today. I had to redesign the enclosure for the interface box to mount in the new shell. Then I had to re-make the linkage pieces since the relative location from the interface box to the throttle changed a bit. Tedious work but not requiring much brain power.

On a related note... I run my throttle and propeller pitch levers through potentiometers then into a Pokeys board. The Pokeys board maps them as two joystick axis which I can then map in DCS to throttle and propeller pitch. I've been getting some jittering in my control inputs. Looking in DCS, just sitting still, you can see the throttle and propeller levers moving back and forth very small amounts. It doesn't affect flying but is annoying all the same. I put a small capacitor across the center tap of the each potentiometer to ground. I had to do it right at the Pokeys board. That eliminated the jittering of the control inputs.

The Gauges are In

The new cables for the gauges are finished so I mounted and connected the gauges. I also finalized the I/O board that drives everything. As you can see from the picture, I still need to dress the cabling behind the instrument panel and I have a few instruments not complete yet. (The stick and rudder pedals are just set in place for now, they aren't mounted yet.)

Trimming it Out

It's nice to fly a well trimmed aircraft. My procedure used to be:

1. Pause the simulation.

2. Dig out the cheat sheet and look up the key command from trimming each direction for the desired axis.

3. Dig out the keyboard.

4. Resume the simulation.

5. Trim the axis from the keyboard while periodically going back to the control stick to keep from crashing, steady the aircraft and determine if the trim needs further adjustment.

6. Repeat for each axis.

All very tedious and immersion breaking. Well now I'm set to make that much more intuitive as I've finished my trim control indicators.

While I patterned them after the P-51 control indicators, I took a few liberties with the design. I made them separate sub assemblies that will mount to the trim pedestal which allows them to be designed and built independent from the trim pedestal. I also wanted protective plastic/glass over the pointer since my pointers will be attached to small stepper motors and I don't want them to be accidentally moved if my hand brushes over them.  The aircraft knobs have the letters inset and painted white. I was able to produce the knobs with the inset lettering, but the paint brush didn't agree with me. It was always a sloppy mess of white paint. I redesigned the knobs to have flat surfaces and just stenciled the lettering in white.

The design concept for each is the same and relatively simple. There is a stepper motor for the indicator and a quadrature encoder for the control input. The rest is just mounting brackets and wiring.

I'm working on the trim pedestal now.  That'll give me a place to mount my new trim control indicators and put them to use.  I've decided to give it a go building the trim pedestal out of aluminum.  It's my first time building out of aluminum so fingers crossed.