SOFTSTART
AND VARIABLE SPEED UNITS.
Overview.
Well
I originally thought I would use “steam hose” as a coupling to make the start
and stop of the motors not so jerky, as mentioned before, it did actually work
but made the drive too “spungy”. I took them out and the drives were too
jerky…. Then researched for some other
way, but it had to be CHEAP.
BINGO…
I found a kit from ‘Disk Smiths Electronics’
(Australia and N.Z.) Their N.Z. site WWW.DSE.CO.NZ
and Aussie site WWW.DSE.COM.AU and have a search for kit No. K3072.
These
units are very robust.. designed to take 12 to 24 volts at up to 20 amps. Ideal
for the windscreen wiper motors that I run.
I
needed 2 for each motor, so that’s 4 altogether. During construction I done a wee modification to allow for FAST
or SLOW “action” but always a slow return. I never really finished wiring
these 2 “action” speeds so my photos
don’t show it but my diagram does. It
goes very well with only 1 action speed so hence my laziness.
I did
however wire up the 2 soft start conditions on each unit. (Quicker to start on
“action”, slower (softer) to start on slow return to center.)
On
studying the circuit for these things, some-one may come up with the idea of
just using one for each motor but I don’t recommend it due to the decay time
required in the electronics and change-over relay spikes.
Above
is the kit assembled… Well after you build it, it should look like this. J
Above
is 2 of them in the one box. Inputs at
the left, output to the motor at the right.
The
relay in the middle is in the “action” circuit and is wired up for 2 different
soft starts…. If the action is coming from the control computer, the relay is
activated to give a shorter soft start, if the sim is going to return to
center, then the “action” circuit is not active and it has a longer soft
start. The difference is with the
amount of capacitance across where C2 on the board. (I took out C2 from the
board and bought out the wires to the relay.. you can see the 2 capacitors for
each board on each side of the relay…. You have to fiddle with the values to
get what you want)
The
other 2 relays (in the top of the picture) are the ones directly feeding the
motors. The have to be heavy enough to take 10 amps on the contacts.
On
the board there is a 7812 12volt
regulator, I tapped into this and bought the 12 volts out for the relays.
All
the relays are just “hot glued” into the unit and the boards are screwed to a
bit of timber and the timber is “hot glued” into the box. I can still get the
boards out if need be by undoing the 2 screws for each one.
In
the picture, the right hand board looks as though it has had a fire… it hasn’t…
its just the photo. !!
A
WORD OF WARNING…. In the instructions the kit mentions a capacitor and a diode
across the motor terminals.. It is VERY important they are fitted BUT NOT TO
THE MOTOR….They get fitted on the output of the board, before the motor relay. If you don’t, the board will blow up sooner
or later… Its for spike protection.
ANOTHER
WORD OF WARNING….NOTHING IN THIS BOX CAN BE EARTHED (To the frame of the sim)…
Remember the motor power supply wasn’t earthed. The reason for this is because
the motors get reversed. Double check
for earthing BEFORE livening it up.
The
above diagram was kindly drawn and donated by Erich.. a great guy and a fellow
builder himself. (Sure beats my hand drawn ones.)
One
day we will see his creation on the net !!
Hint … hint …. Erich ! !
Thanks heaps Erich.
You
can download this circuit for printing out if you like… here… www.jimspage.co.nz/variscan3.zip
I
did not wire up the external connections to VR1.. I just used the preset on the
board.
CONCLUSION.
These
worked very well and are really the heart of the sensation of motion. They take away any jerking etc and are quite
adaptable for various types of starts or speeds.
IF
I WERE TO BUILD THIS AGAIN ?
Yes, I would definitely use them again. I can’t see what would be better, cheaper or easier than these units.
Updated 1-1-06