Wiring a New Electronic Controller for a Vintage Sewing Machine.

First, let me clear up a few myths about electronic controllers. They do NOT increase the piercing power of the machine in any way, shape or form.  All that they do is control the watts (amount of energy (joules) per second) going to the motor.  More watts = more speed, less watts = slower speed, and no watts  = stopped. 

So, why would someone want an electronic controller?  Because they don't produce heat as they regulate the electrical flow to the motor. If you have a habit of never completely removing your foot from a mechanical resistor type controller (carbon pile or wire wound type), these controllers can get VERY toasty. Why? In simple terms,  they take the electricity that they are not sending to the motor and turn it into heat. So if you leave the controller just barely engaged, it may not send enough power to the motor to actually move it, but it will convert the remaining 99% of the electrical flow into heat.  Likewise, if a mechanical resistor type controller malfunctions or isn't adjusted properly, it can get excessively warm, even hot.  An electronic controller approaches the regulation of electrical flow differently and eliminates this problem. The down side to the electronic controllers is that they are plastic, and feel flimsy compared to some of the other controllers.

If you do not have the proper tools, knowledge or experience to complete this project in a safe manner, for goodness sake, DON'T DO IT.  Never work on any electrical item while it is plugged in to a power source.  I am not responsible for any problems that you may encounter as a result of attempting this project.  PROCEED AT YOUR OWN RISK. 

Do not use any magnetized or magnetic tools in conjuction with the PC board or any of the screws on the PC board. (Many screw drivers have magnetic tips)

For this project, I started with these items- a new electronic controller and a new Singer, double lead cord set.
   There are different styles of electronic controllers. This article will show how to rewire two of them.

The first style is shown to the left and is the easiest to work with. The top screws onto the base, no extra cord strain relief is needed, and it utilizes the more standard ring or fork type wire terminals found on most existing and new cord sets.
As you can see in the photo, I do add a short length of heat shrink tubing over the cord where it enters / exists the controller body.  This is optional, but does give the cord a little extra support and strength.

This style controller is about the same size as the Singer button controller, but much lighter.


Below is the process I use when wiring up one of the more compact, replacement, electronic controllers:
I also used a strain relief plastic plug gizmo do-hicky. 

Some hardware stores sell them, but finding the right size/shape for the controller isn't always all that easy. I will be carrying them on my parts site. 

Now, let me say that installing these isn't all that easy the first few times, but with practice I have learned exactly which cuss words seem to line everything up  just right.  In the end through, the nice professional, factory look of the installation makes it worth the effort.  
  Tools: Wire cutters, wire strippers, wire crimping tool.

To the left - the connector that comes on the new cord set. and one cut wire.

OK, the first thing to do is to remove the terminals from the end of the wires on your cord set.  You'll need a "special" type for the electronic controllers (female spade terminal).  The controller comes with These "special" terminal ends, but I prefer some that I find at my local hardware store.  Either ones will work fine.

  Pop the top off of the controller.  Determine how much wire you will need inside the controller.  Put the strain relief around the wire at the desired spot and push it into the hole. Implement the  required cuss words to get it to fit.  Then, connect the wires onto the board inside the controller. 
Here it is all done, except for popping the top back on.  I use the silver colored square-ish piece as a sort of clip to add some extra strength to the security of the strain relief. It just makes it all that much more stable.
See how nice that looks? It's all put back together and ready to use. 

I have cord sets and controllers in stock at the Sew-Classic Parts & Supply online store, Shop.Sew-Classic.com

Geek type notes: 
  • The 120 VAC in the USA is a nominal figure and it IS the RMS (root mean square) or effective value.
  • Watts = Amps x Volts.

  • Trackbacks are closed for this post.
Page: 1 of 1
  • Wednesday, January 13. 2010 Diana wrote:
    Oh Jenny....you inspire me. I will start a list of the proper cusswords so I will be prepared to make the changeover!!!
  • Saturday, January 30. 2010 IdaMay wrote:
    Interesting and thorough article, thank you!

    Is there any possibility of putting the electronic circuit board into my 403's mechanical resistor type controller? I would like to continue to use the knee control option of my cabinet.
    1. Sunday, January 31. 2010 Sew-Classic wrote:

      "Is there any possibility of putting the electronic circuit board into my 403's mechanical resistor type controller? I would like to continue to use the knee control option of my cabinet."
      Nope.  I doubt you can retrofit the innards of an electronic controller into a singer button controller. HOWEVER, I did mount an electronic controller to the spot where the controller bracket would go inside of a Signer cabinet once. I used velcro.   The mechanism for the knee bar simply pushed on the electronic controller directly.  I do not have any pictures or a tutorial written, but it wasn't rocket science.  Stick your head under the cabinet and see how the knee lever works and you should get the idea.

  • Saturday, February 06. 2010 Steve B. wrote:

    I disagree about the "NOT increasing" statement.

    An electronic foot pedal is a pulse width modulator (PWM). What it does is rapidly pulse the motor with very narrow, but full power supply voltage pulses. The farther down you press on the foot control, the wider (in time) these pulses become, hence more motor speed.

    You are right when you state the advantage of not producing any discernable heat, but the PWM control will give you considerably more motor torque at low speed. This translates to more piercing power as well a smoother start up speed control.

    Steve B.
    Certified Bernina Technician
    (and retired electronics repair tech)
    1. Saturday, February 06. 2010 Sew-Classic wrote:

      OK, lets look at two identical sewing machine motors, both running at 1/8 of full speed at the exact same RPM.  One motor is regulated with a carbon pile controller, and the other is regulated with an electronic controller. 

      Now, the mechanical energy output of the motors is directly proportional  to the speed/ RPM and the energy input in terms of watts (joule per second).  So, since both motors are operating at the same speed, they both are drawing the same amount of amps/watts AND producing the exact same amount of mechanical energy (output).  

      If the mechanical output of the motor regulated by the electronic controller was indeed "stronger",  then the motor would simply be operating at a higher RPM. The power output of the motor is solely and directly related to the power input.  Again more power (watts) in = more speed= more power out. 

      Furthermore I have used both electronic controllers and carbon pile controllers on the exact same machine.  Granted, I do not have any sort of "dynamometer" to connect to the needle, but there was NEVER any difference in piercing power or top speed of the motor using the different types of controllers. 


      On the universal type motors used on vintage and some newer sewing machines,  the torque remains nearly constant regardless of the motor speed.  However, the power output (horsepower) increases as the RPM (speed) of the motor increases. 

      = rpm x T(torque)

      Certified Independent Thinker

      1. Sunday, February 07. 2010 Steve B. wrote:
        You are right about the RPM in a no load situation, but we're talking about torque under load.

        A better example would be a power drill or hand operated grinder with a PWM variable speed control trigger. You have considerable torque at low speed, an application which wasn't possible until the advent of electronics for the control. With a resistor in series to a drill motor at low rpm, you wouldn't have anywhere near as much torque.

        Full power torque and RPM either case would be the same.

        For years, Bernina has stated the low speed torque advantages of electronic control and DC motors.

        Here's one line from a PWM circuit design I found by searching for motor torque PWM vs resistive control:

        "One additional advantage of pulse width modulation is that the pulses reach the full supply voltage and will produce more torque in a motor by being able to overcome the internal motor resistances more easily."

        1. Sunday, February 07. 2010 Sew-Classic wrote:
          The internal motor resistances are yet another constant regardless of speed, or energy input.

          Any advantage of the full pulse of electrical energy is immediately offset by the momentary complete loss of power as the pulse stops.  This cessation of power is what allows the universal sewing machine motor to run at anything other than full bore 100% top speed with the electronic controllers.

          The motors on these vintage machines ( and some new sewing machines) are a universal type motor with brushes that will technically operate on either DC or AC power supply.  These types of motors have nearly the same torque level at all speeds, low, middle and high,  constant torque regardless of RPM.  The internal load on the motor is also a non variable constant, but once the motor RPM increase, kinetic energy will certainly play a role. The power output/hoursepower does increase as the RPM increases.  It is for these types of motors that the 2 wire replacement electronic controllers are to be applied.

          None of this has anything to do with Berninas market and sales information with regard to their DC motors or electronic controls- completely different beast, and is not the least bit relevant to the replacement of controllers on vintage machines. 

          Bottomline, on the universal motors to which these electronic controllers are to be connected, more power input will directly tranlate into more speed and more power output.  So, if the electronic controller provides the motor with more power, it will simply spin faster.  The torque on these motors is CONSTANT, and as RPM's increase, so does the horsepower and mechanical power output of the motors.  The above statement also applies to the carbon pile controllers, more power (juice)= more speed = more horsepower.

          Furthermore, I have done controlled, side by side comparisons with the ONLY variable being the controller, and there is ABSOLUTELY NO DISCERNIBLE INCREASE OR DECREASE OF PIERCING POWER BETWEEN THE ELECTRONIC AND CARBON PILE CONTROLLER.

          So, you are more than welcome to your thoughts and ideas, but not only do the facts not support the contention that an electronic controller will somehow magically give a sewing machine with an universal type motor more piercing power, but practical real life comparison has also proven it.  this is the gist of my statement in this blog entry- and electronic controller will not give your machine more piercing power.   
          1. Thursday, February 18. 2010 L J Parker wrote:
            What Steve did not get across is that the electronic pulse width controller gives variable duration of FULL voltage to the motor. For example with both controllers running full on, both motors get 120VAC if that is your power. With pulse width modulation (PWM), as starting to run position, the motor gets pulses of 120VAC while the resistance controller is giving about 50VAC full time. The Higher torque on the PWM unit is due to getting that full power. Me, I'm a purist. My machine came with a carbon pile controller that went bad, it gets another carbon pile controller. Ole L J
            1. Thursday, February 18. 2010 Sew-Classic wrote:

              A couple of very basic principles here.

              The amount of mechanical energy put out by these motors is proportional to the amount put in (watts), and as the amount of energy going in increases, so does the RPM.

              You need to look at the WATTS (joule per second) being deliveed to/used by the motor.   

              The machines do have more piercing power at the needle as the machine and motor speed increases due to a couple of factors. One being the role of the kinetic energy developed with the rotating masses of the machine itself, and the other being that as RPM's increase, so does horsepower. (see the mathematical formula referenced to above)

              OK, So, with the PWM the speed is controller by pulses of full power, followed by periods of NO POWER.  I can demonstrate mathematically how these would offset each other, but I don't think that is really necessary.  You are absolutely correct that more watts being drawn or delivered to the motor will allow the motor to produce more mechanical power, and it is very simple to be aware of any increases of watts going into the motor by the change in RPM’s. More watts (jole per second) in translates directly to an increase in RPM’s.

              Beyond the theoretical debate, comes the “proof in the pudding“- practical application. To that end,  I HAVE USED THE SAME MOTOR ON THE SAME MACHINE WITH BOTH ELECTRONIC AND CARBON PILE CONTROLLERS. THERE WAS NO, I REPEAT, ABSOLUTELY NO, PERCEIVABLE DIFFERENCE INT HE PIERCING POWER OF THE MACHINE. None, nadda, zilch.

              ETA, an engineering friend of mine asked me to add the following:

              Full power bursts from an electronic controller plus zero power bursts
              continuous partial power from a resistor controller
              same machine RPM
              EQUALS the same power. 
              (torque is a component of power)

              My engineer friend thought this simplified version might clear up the confusion.

  • Sunday, February 07. 2010 Steve B. wrote:
    I never said it would give a motor more power, just that it would have more torque at low speeds.

    Believe what you want, I'm done with this discussion.
  • Monday, March 22. 2010 Don wrote:
    Would I be able to use this controller for a 220V machine? I notice that the circuit board shown in one of the photographs is printed with both 120V and 220V (although the 120V has a check mark next to it). Is this simply a fuse replacement, ot is this controller only for 120V use?
    1. Tuesday, March 23. 2010 Sew-Classic wrote:
      Both controllers are specified for use at 120 VAC.  I can order 220 volts versions.  Just contact me directly and drop me a note.
  • Thursday, September 02. 2010 Steve wrote:
    Looking at the innards of both of the controllers illustrated above I don't believe the first example is a PWM controller, am I wrong? There isn't enough circuitry to be PWM controller. If I am incorrect on this, can anyone direct me to WHICH of the foot pedals sold here on this site are PWM and which are not please?

Page: 1 of 1
Leave a comment

Comments are closed.