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Posted by Ron on May 2, 2008, 6:43 am
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I do not mean to rain on anyones parade. But, there is a
potential problem using single pole starter relays in this
circuit.
If the relays with suppression diodes drop out slower than
they pull in, you could have an overlap situation where both
k1 and k2 for instance are closed at the same time.
This could cause a very high current pulse which would blow
the fuse and could weld the contacts on the relays.
This would only happen if someone were to flip the control
switch quickly from cover on to cover off or vice versa
without a pause in the center off position.
The easiest way around this would be to use a switch that
forces you to release pressure on the lever while in the
center off position before it will allow you to proceed to
the other position.
Such switches are made. Unfortunately, I don't remember who
makes them or who sells them.
The timing of the particular relays that you use may not
present this problem. But, it is something to check before
turning the system over to the user.
Ron
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Posted by Carl Boyd on May 2, 2008, 7:41 am
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Good Catch!
Carl Boyd
>
> I do not mean to rain on anyones parade. But, there is a potential problem
> using single pole starter relays in this circuit.
>
> If the relays with suppression diodes drop out slower than they pull in,
> you could have an overlap situation where both k1 and k2 for instance are
> closed at the same time.
>
> This could cause a very high current pulse which would blow the fuse and
> could weld the contacts on the relays.
>
> This would only happen if someone were to flip the control switch quickly
> from cover on to cover off or vice versa without a pause in the center off
> position.
>
> The easiest way around this would be to use a switch that forces you to
> release pressure on the lever while in the center off position before it
> will allow you to proceed to the other position.
>
> Such switches are made. Unfortunately, I don't remember who makes them or
> who sells them.
>
> The timing of the particular relays that you use may not present this
> problem. But, it is something to check before turning the system over to
> the user.
>
> Ron
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Posted by Pete C. on May 2, 2008, 7:56 am
Please log in for more thread options
Carl Boyd wrote:
>
> Good Catch!
>
> Carl Boyd
>
> >
> > I do not mean to rain on anyones parade. But, there is a potential problem
> > using single pole starter relays in this circuit.
> >
> > If the relays with suppression diodes drop out slower than they pull in,
> > you could have an overlap situation where both k1 and k2 for instance are
> > closed at the same time.
> >
> > This could cause a very high current pulse which would blow the fuse and
> > could weld the contacts on the relays.
> >
> > This would only happen if someone were to flip the control switch quickly
> > from cover on to cover off or vice versa without a pause in the center off
> > position.
> >
> > The easiest way around this would be to use a switch that forces you to
> > release pressure on the lever while in the center off position before it
> > will allow you to proceed to the other position.
> >
> > Such switches are made. Unfortunately, I don't remember who makes them or
> > who sells them.
> >
> > The timing of the particular relays that you use may not present this
> > problem. But, it is something to check before turning the system over to
> > the user.
> >
> > Ron
Just use one of the remote solenoid upgrade kits that are sold by winch
manufacturers such as Warn, Ramsey, SuperWinch, etc. as upgrades for the
base model winches that come with local switches. Fast, simple, compact
and designed and tested for the application.
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Posted by James Waldby on May 2, 2008, 11:58 am
Please log in for more thread options On Fri, 02 May 2008 06:42:53 +0000, Winston wrote:
> Don Foreman wrote:
>> On Thu, 01 May 2008 19:05:20 -0600, gary556@... wrote:
>>>I'm trying to wire a Freightliner to operate the tarp motor.
...
>> If you use starter solenoids, you'll need four of them if you want it
>> to run in both directions. The switch can be a SPDT center off or DPDT
>> center off toggle switch. The solenoids would be arranged in an H
>> with top of the H going to + battery and bottom of H going to ground or
>> - battery with the motor being the crossbar of the H.
>>
>> -----------
>> | |
>> S1 S3
>> |--M--|
>> S4 S2
>> | |
>> -----------
>>
>> The switch would then energize diagonally opposed pairs of solenoids S1
>> and S2 or S3 and S4, one set for up and the other set for down.
...
> http://metalworking.com/dropbox/tarp.txt
> http://metalworking.com/dropbox/tarp.JPG
>
> On the right side you see a three position switch. Select 'Tarp On' and
> the motor drives the tarp over the load. The limit switch stops the
> motor when the tarp is in place. Select 'Tarp Off' and the motor removes
> the tarp from the load. The other limit switch stops the motor when the
> tarp is off.
...
Some other posts have said to just use a switch rather than switch +
relays; 20A 12V DPDT center-off switches are readily available, eg
http://www.parts-express.com/pe/showdetl.cfm?partnumber=060-376 or page
89 of http://www.delcity.net/delcity/documents/catalog/9_switches.pdf
if 20A is enough for the tarp motor. Of course if the limit switches
aren't heavy enough to switch the motor, you'd need relays anyway.
Note that in the dropbox/tarp.JPG diagram, the K3 and K4 coils are
shown backwards. Hooked up as shown, the internal diodes or the
wiring to them would burn up on first use.
-jiw
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Posted by Winston on May 2, 2008, 6:28 pm
Please log in for more thread options James Waldby wrote:
> Some other posts have said to just use a switch rather than switch +
> relays; 20A 12V DPDT center-off switches are readily available, eg
> http://www.parts-express.com/pe/showdetl.cfm?partnumber=060-376 or page
> 89 of http://www.delcity.net/delcity/documents/catalog/9_switches.pdf
> if 20A is enough for the tarp motor. Of course if the limit switches
> aren't heavy enough to switch the motor, you'd need relays anyway.
Those are A.C. rated at 20A. A switch rated properly is a different
animal altogether. Bigger and more expensive.
Can you tell me the part number for a DPDT center off switch capable of
handling locked rotor current, cheaply?
Using the relays allows one to use relatively light gauge wire to connect
the control panel to the motor and the limit switches, as you implied.
> Note that in the dropbox/tarp.JPG diagram, the K3 and K4 coils are
> shown backwards. Hooked up as shown, the internal diodes or the
> wiring to them would burn up on first use.
Good catch! Thanks, James! Corrected version is posted.
http://metalworking.com/dropbox/tarp_a.JPG
http://metalworking.com/dropbox/tarp_a.txt
--Winston
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> I do not mean to rain on anyones parade. But, there is a potential problem
> using single pole starter relays in this circuit.
>
> If the relays with suppression diodes drop out slower than they pull in,
> you could have an overlap situation where both k1 and k2 for instance are
> closed at the same time.
>
> This could cause a very high current pulse which would blow the fuse and
> could weld the contacts on the relays.
>
> This would only happen if someone were to flip the control switch quickly
> from cover on to cover off or vice versa without a pause in the center off
> position.
>
> The easiest way around this would be to use a switch that forces you to
> release pressure on the lever while in the center off position before it
> will allow you to proceed to the other position.
>
> Such switches are made. Unfortunately, I don't remember who makes them or
> who sells them.
>
> The timing of the particular relays that you use may not present this
> problem. But, it is something to check before turning the system over to
> the user.
>
> Ron