Surplus stepper motors in UK

Ebay, or from old printers

I have come to the conclusion that with the improvements in magnetic materials surplus steppers unless real cheap, which they never are, are a waste of time. For what you are asking secondhand, 300 oz in this falls into the type

34 motor domain and you will be pushed to find something 5v at 2 amps that's a true 300 oz in.

I have a round series Centronics 340 oz in 34 motor here 5 volts at

4.8 amps and to be honest it's not that great compared to the newer square double and triple stack motors.

With apologies for making a blatant advert, no sod it why should I apologise, Arc Euro seem to be on the ball selling late spec motors at reasonable rates. That much so that they are often cheaper than S/H ones on Ebay.

They are advertising a 220Ncm, that's 311oz in in a type 23 frame,7.5v, 2.5A for £39.50 inc

These modern square motors are far superior in size and power to many of the original motors. Some may be aware of the large finned motors fitted to the Bridgeport BOSS series often favoured by colleges and finding their way onto the cheap secondhand market. Hard to drive with low cost drivers as these often require up to 12 amps. These are large type 42 motors either direct driving onto ball screws or 2:1 reduction. Even though these are massive motors in terms of size and amperage they are rated at 850 oz/in.

Looking on Arc Euro site they list a 34 motor, 650 Ncm or 920 oz/in 5 volt, 4.2 amp which is well within most cheap drivers so you are getting a far bigger motor for less power.

Web site with details.

Regards,

John Stevenson Nottingham, England.

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Many thanks John. Having searched for a few days now, I am surprised that I missed these guys....I like their prices and seems to fit the bill perfect. At 7.5V I guess its still possible to overdrive them with a 'chopper' type supply.

John.

Certainly is. They also sell chopper drives at decent prices - there's one that will handle up to 3A/40V and also an 8A/80V drive. I have used the bigger ones & they perform very well.

Regards, Tony

You need to overdrive steppers. That 7.5 volts is the operating voltage but it has to get up to power. You need to use a higher voltage to get speed. Within design limits volts are speed, amps are torque Older drives worked by overpowering and then dumping excess power down into ballast resistors., works but wasteful.

Newer chopper drives work by over supplying with volts and then as the limit is reached they switch off, then back on, then off many times a second.

Stepper power supplies follow a laid down guide line for voltages and capacitor sizing. Rule of thumb is to supply the motor with 20 times it's rated motor voltage provided that this doesn't exceed the driver voltage. In this case your motor is 7.5 volts so rule of thumb says up to 150 volts but the drivers are rated at 40 volts.

It never pays to run at close to driver voltage for safety reasons. In this case a 24 volt transformer x 1.414 to get to DC will give 34 volts which is a nice high figure but inside the design limits of the driver.

Good news is it's not all ear of bat, tongue of newt as people have done this all before. Have a read here.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-