I have acquired a small surplus stepper motor and gearbox. I spoke to
the makers of the gearbox (Weyer Bros Ltd), and they inform me that
the motor was made about 20 years ago by a company called Cauldron
which is no longer trading. Later, another company called Julius Sax
made the same motor, but I understand that they have disappeared too.
Unfortunately they could not give me any help regarding the motor, but
they did say that they have had several similar enquiries in the past.
Does anyone have any information and/or suggestions for a suitable
driver board? The motor has the following limited markings:
Type C115, Supply Voltage 28v dc, Steps/rev 10
The connection lead colours are Black, Green, Red, Blue and Orange
How can I determine which lead is which?
Any help would be very much appreciated.
because the motor has 5 wires, it's almost certainly a unipolar type. So you
need to look for a unipolar stepper motor driver.
This link might help you to figure out which wire is which;
I hope this helps,
On 4 Nov 2004 01:24:46 -0800, email@example.com (TonyK)
If it is a 5-wire, unipolar motor (which seems likely), then it will
be "star wired" with one of the four wires at the centre of the star
and the other 4 at the points. If you measure the resistance between
pairs of wires, you will find one wire for which the resistance to
each of the other 4 is the same; this wire is connected to the centre
of the star. The other 4 are connected to the points; you will find
that the resistance between any two of these four is near enough twice
the resistance between any one of the four and the centre wire.
(By the way, if you find that, for each wire, there are two wires to
which the resistance is R and two wires to which the resistance is
near enough 2R, then what you have is a 5-phase motor with the phases
connected in a ring, and all bets are off as the drivers for these are
probably going to be more expensive than tossing the motor and buying
a conventional stepper and driver. However, this is unlikely.)
Unfortunately, the four coils of the motor are paired; it isn't at all
obvious how to determine the pairings in a 5 wire motor (or an 8 wire
motor, for that matter). Think of the 5-wire unipolar motor as having
two centre-tapped windings, as in a 6-wire stepper, but with the
centre taps strapped together; what you are trying to discover is
which of the "points" are connected to each end of the two windings.
If you don't get this right, the motor won't run.
One method that I have heard of (but not tried) goes as follows:
Number the wires 1 through 5, where 1 is the centre of the star.
Connect a power supply of suitable voltage/current (doesn't need to be
the full 28 volts for this) with the +ve to wire 1 and the -ve to wire
2. The rotor may step to a new position if the rotor was not already
at the right step position. Disconnect the supply; the rotor should
stay put. Re-connect the supply, this time with the +ve to wire 3 and
the -ve to wire 1.
If the rotor stays in the same step position, then you have found the
2 end points of one winding (and the other 2 wires, 4 and 5, are the
endpoints of the other winding).
If the rotor steps to a new position, then you know that wires 2 and 3
are endpoints of different windings; repeat the process using wires 1,
2, and 4, and at that point, it is possible to work out what the
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