All switches are un-powered dry contact devices.
All grade 1 switches can control 0.05 amps at 12 VDC
All grade 2 switches can control 3.00 amps at 12 VDC
All grade 3 switches can control 5.00 amps at 12 VDC
All switch holders plates must center switches on the 0.5 inch Meccano system specification
Switch holes must be 7/32 diameter.
Level 0 switches are dry contact switches
Level 1 switches use power. ie A photoelectric switch.
All motors must be designed for running at 12 VDC though they will actually be run on PWM systems operating at 24 volts. This makes it easier to get power out of the motors under load.
Permanent magnet motors are preferred as needing less power and being easier to reverse
Brush type motors are preferred as less expensive
All grade 1 motors draw less than 1.00 amps at 12 VDC
All grade 2 motors draw less than 3.00 amps at 12 VDC
All grade 3 motors draw less than 5.00 amps at 12 VDC
All motors shall be reversible by reversing the current to the motor either with a computer or with a DPDT switch/relay.
The limit on motor torque is the power that can be transmitted by a screw tightened onto the 0.157 inch diameter shafts of the Meccano system. Extra torque can be destructive in our system. An 5 amp motor at 12 VDC is pretty much too powerful for Meccano but can proved a large torque at low speeds when controlled with an appropriate PWM (Pulse Width Modulated) signal. Thus the grade 3 designation does make some limited sense.
Motor shaft specifications
0.1575 inch diameter by 5/8 inch long
A flat on the motor shaft is optional but is recommended on grade 2 and 3 motors
Meccano Specifications (are generally agreed to be as follows)
Hole spacing 0.500 inches
Hole size 0.160 inches diameter
Shaft size 0.1575 inches or 4 mm.
This is very close to 5/32 inches or 0.1563 inches. Works OK
Material Stainless steel rods and shafts are preferred.
Galvanized shafts as are provided by Meccano are of course OK.
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Any computer with serial USB-1 communications interface can control the hardware. We may want to also think about the older RS-232C interface also.
Both the Macintosh and Wintel computers must be able to support the software.
Other computers can be supported by the group as they may decide as time goes by..
09 Apr 04