Modernising the electronics of a vintage Singer 99k sewing machine

As I mentioned in my previous post when I was restoring the sewing machine, the electronics were in a pretty bad state.

I believe the pedal was meant to allow for variable speed input, but in reality it acted just like a simple on/off switch, and pressing the pedal down the whole way tripped the circuit breaker.

Inside the motor housing once
the rotor had been removed.

Initially I tried just repairing what was there, replacing brushes in the motor, cleaning it all up – which seemed to provide some temporary improvement but it soon deteriorated again.

 

 

 

 

 

 

So I decided to just try and replace all of the electronics with modern equipment, but retained the original casings to try and maintain the rustic aesthetic. I figured with modern advances in electronics it is quite likely that a lower power, modern motor would be able to provide comparable performance to the old one (the analogy that springs to mind is the state of modern cordless power tools versus old mains powered ones).

It is clear that the original motor does not have any kind of gearing to boost power – the circuit seemed to be about as basic and simple as it gets.

As I was researching the old motors I did see some mention about potential asbestos hazards – this is near the bushings of the motor – it is intended to support the bushing and act like a self-centering bearing. As I am entirely replacing the motor I had no need for it. With appropriate protective equipment in place I was able to remove it and dispose of it appropriately.

There was also mention about the being asbestos washers in the foot pedal, however my one does not appear to have these – but nonetheless I will not be using this pedal anyway.

One side the case of the me to opened up I was able to pull out the coil windings and rotor, leaving an empty shell. I removed the original connectors.

 

The screwdriver
To replace the motor I am going to use a cheap cordless screwdriver. Being cordless it should be adaptable to run on a lower power, but given the task that it is designed for, it should still be able to provide enough torque to run the machine due to it’s gearing set up.

In these cordless screwdrivers all the electronics tends to be in the handle, so it is easy to separate out the motor and gearing system from the rest of the device.

With that done I needed to trim off some of the casing to get it to a suitable size to fit in the sewing machine motor case. 

The only modification I needed to make to the sewing machines motor case was to drill out the opening slightly as the shaft of the screwdriver was a little bit wider, however this is not actually visible from the exterior.

To mount the screwdriver, I 3D printed a mount (Github/Thingiverse).

It's simply a friction-fit wedge that goes around the screwdriver body and into the sewing machines original metal case. 

The diameter of the shaft of the motor is the same as the original motors pulley, but worth bearing in mind that the new motor is slower. I had the idea to increase the diameter of the shaft, in order to change the gearing between the motor and the sewing machine and get a bit of a speed increase. It should also increase the grip on the pulley as there will be a larger surface area of the belt in contact with the shaft.

 

 

To do this I created this (Github/Thingiverse). It fits within a small section of aluminium tube (to prevent wear on the plastic), and over the shaft of the screwdriver. It's locked in place with an allen key (cut flush) that fits as if it were a screwdriver bit and locks into this plastic widget. Finally I locked it all together with some adhesive and wrapped a bit of grip-tape around the aluminium. 

Driving and control
To drive a motor I am using a BTS7960 motor driver, controlled by an Arduino (for now, for the purposes of prototyping).

Simply this will be an analog input, which the arduino will translate into pulse width modulation (PWM) and send to the motor driver. This is possibly overkill, but the priority at the moment is too get the machine working – optimization & improvements can come later.

For now, I have a simple potentiometer to set the PWM, and the pedal is actually just a switch cable tied to the legs of the sewing machine. I am hoping to be able to get a treadle foot pedal like those that would have traditionally been part of the table legs that I’m using, and use that – if I’m ever able to find one.

Pulley Belt
The belt connecting the motor to the machine was worn through and hanging on by a thread, so it needed replacing.

There seems to be a lot of various DIY how-to ways suggested to create pulley belts to size, so I started working through those. The results were:

• Pulley belt from an old printer cut to size and stitched together using fishing wire - failed - snapped.
• As above, but joined with glue and stitched - snapped.
• Electrical wire (speaker cable) threaded together, and heat-shrunk to provide a rubberised grip. This seemed promising - it didn't snap at least, but the heat shrink, although intended to provide grip, seemed to have the opposite effect.

After all that, as a temporary measure, I joined 3 nylon cable ties together, just so I could move on to the rest of the project. And as the saying goes "There's nothing more permanent than a temporary fix", it's still going strong.

 

Light
The motor housing also contained a small lamp fitting. This was previously a mains powered, incandescent, bayonet fitting bulb. However I rewired and replaced this with a 12v LED bulb – much in the same way the I did with the Sunset Sarsaparilla lamp project.
 

 

Power
Power was provided by an old desktop computer power supply. This provides 12v lines for driving the motor and the light, and 5v for the logic. Again, this is another quick prototyping move, and will eventually be replaced by something nicer.

Finally all that was left was to oil the machine as indicated in the original manual, and give it a try.

 

 

View this post on Instagram

A post shared by Anthony (@darkmidnight_diy)

Yarn slack winder

This is another of the lockdown projects where I'm trying to keep myself occupied during the Covid-19 lockdown by challenging myself to a project per week, using only materials from my workshop junk bin.


Background
I don't crochet or knit, but my partner does, and I often end up watching TV whilst having been delegated to idly unwinding a ball of wool.

So, apparently, when crocheting or knitting, it's important to make sure that there's some slack between the workpiece and the ball of yarn. This usually means stopping every so often to pull more yarn from the ball. It can lead to inconsistent tension in the workpiece, making the work uneven.

This gave me an idea to create a yarn dispenser that could be hands-free, and unwind small amounts at a time, to maintain slack.

The OpenSCAD model

The design

The basic principle is to repurpose two rubber rollers (grey) from a printer. The bottom one is attached to a motor, which is housed in the case (red), and supported at the other wide by a support (yellow).
The top roller is attached to two mounts (blue) and is free-rolling.

The two mounts will be attached to their respective parts of the case by screws, where the tightness can be adjusted to allow more or less gap between the rollers, to vary the grip depending on the thickness/density of the yarn.
 
The yarn will be sandwiched between the two rollers, so that when the motor is activated by a foot pedal, it is pulled between the rollers.

To keep the two sides of the frame separate, they were mounted to a small piece of scrap acrylic I found. It's not a perfect size, but it's functional enough for this prototype.

The 3D printed models are pretty basic, but should anyone want to use them, they're up on GitHub.



The electronics

The motor is some generic DC motor that, like most things in the junk bin, was probably pulled from an old printer.

Most of the circuit for this was was salvaged from the old Smoke Machine project.

The SN754410 was de-soldered so that it would function in a more conventional way, powered from a 9v wall wart, and a TS7805 regular to provide 5v.

The circuit. The SW1 switch allows the direction of the motor to be easily switched. SW2 is the foot pedal that will be pressed to feed the yarn.

The electronics were built into an old business card box, similar to the USB KVM Switch.

With the circuit hot glued in place, a piece of a disposable pen was glued to the button to extend it's reach, so that it would sit slightly higher than the top of the box lid. This means the the circuit enclosure also doubles up as the foot pedal - pushing down on the lid pushes on the pen, and in turn presses the switch.

Finished product
In initial testing, it was discovered that the yarn would veer off to the side of the rollers and become tangled. As a quick-fix solution, I used a scrap of leather, punched a guide hole in the middle and tacked it to the input side of the rollers.

View this post on Instagram

A foot pedal activated yarn winder to maintain slack when knitting or crocheting. My second "lockdown project" - 1 week builds using only items I have to hand. #electronics #3dprinting #diy #upcycled #reclaimed #knitting #crochet

A post shared by Anthony (@darkmidnight_diy) on Apr 30, 2020 at 2:33pm PDT

Wiring an interface to an e-Cigarette

I'm currently working on a project that requires the use of an e-cigarette.
I'm not a smoker, so as far as that aspect is concerned, I might be a little off on the terminology, but eCigarettes, vapourisers, whatever you want to call them, essentially follow the same principle. There's a battery, a small reservoir of vaping fluid, a wick, and a wire coil.


Current is passed through a coil which causes it to heat up, in turn heating a wick soaked in fluid which turns it into a vapour.
We can ignore the battery component, it's only really the wire coil I need for the project. I do however need to control it, so I needed to find a way to interface it.



The coil connects to the battery by a screw-type connector which appears to be specifically for these devices. In addition, the connector also contains a small gap which acts as an air inlet for the user to take a drag on it.

This causes problems when trying to create a connection, as connectors run the risk of blocking the inlet.

Coincidentally I found that a male TV aerial connector is an ideal size to create a push-fit connector. The next task is to decide how to control the current flow. Simply switching it on and leaving it will cause it to overheat.


Coils like this can be controlled in similar way to motors. In fact, the IC I'm going to use to control this is really designed for driving motors, but works fine for the purpose of this.

The chip is the SN754410 H-Bridge motor driver - which is completely overkill for this, but as this is forming a part of a larger project, the reasoning will become clearer later.

The pinout for the chip is available on the third page of this datasheet. Treat the vapouriser as if it was a motor - polarity/direction of travel doesn't matter.

For the motor drivers voltage I'm using 12v, which, again, is overkill for this part in particular, but the coils are very tolerant of it, and use the speed control function of the chip to control how hot the coil gets.

That's all for now, stay tuned for the 2nd part of this project...