BoatBanter.com - Power Transister or Relays??

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Power Transister or Relays??

I finally located a stronger 12 volt linear drive unit for the tiller pilot
on my 13 ton Ingrid 38. It has all the power and length of stroke that I
feel I need (when the going gets tough).

This unit has a 14" stroke (stop to stop) 1000# dynamic, 1500# static and
overload clutch rated at 1200-1600# w/auto thermal overload.

However; the drive motors max current draw is 14 amps.. Now that sounds like
a lot but under normal operating conditions it shouldn't take more than 5-6
amps and then only in pulses since the tiller load is normally fairly light.
(from my observations of the AP performance recently, the duty cycle is
about 1sec on/15sec off. ) Under heavy conditions, I'm sure this will be
different and I have not data since the tiller load is too great for the OEM
linear drive.

I will be using this AP set up mostly while motoring so power consumption
will not be a primary factor.

I will still be using the very reliable AH3000 tiller pilot control head but
since this unit is limit to only a couple amps output to the old linear
drive, I need to build a power controller circuit (not sure that the right
term), to deliver the full 14 amps to the new linear drive motor.

Both the old and the new linear drive was controlled by the switching of
polarity to the drive motor. I would use this same output from the control
head to switch the output polarity of the power controller..

First I would like to know which would be the most effiecent and reliable,
Transistors or Relays in this controller.?? I realize I could build it from
regular, off the shelf automotive relays and if they fail, I can just plug
in a spare, but then if I mount my transistors in sockets, I could do the
same thing.

BTW. Either controller will be protected, below deck in a sealed box.

Can anyone offer a curcuit diagram for either transistor or the rely power
controller. I'm not an elex. whiz but I can build just about anything that
you guyz can sketch up for me. Or a good reference that might have such a
circuit.

Thanks,

Steve
s/v Good Intentions

Power Transister or Relays??

Steve,

I would use neither. MOSFETs would be my choice. Check out
International Rectifier's website.

Doug

"Steve" wrote in message
...
I finally located a stronger 12 volt linear drive unit for the tiller
pilot
on my 13 ton Ingrid 38. It has all the power and length of stroke that I
feel I need (when the going gets tough).

This unit has a 14" stroke (stop to stop) 1000# dynamic, 1500# static and
overload clutch rated at 1200-1600# w/auto thermal overload.

However; the drive motors max current draw is 14 amps.. Now that sounds
like
a lot but under normal operating conditions it shouldn't take more than
5-6
amps and then only in pulses since the tiller load is normally fairly
light.
(from my observations of the AP performance recently, the duty cycle is
about 1sec on/15sec off. ) Under heavy conditions, I'm sure this will be
different and I have not data since the tiller load is too great for the
OEM
linear drive.

I will be using this AP set up mostly while motoring so power consumption
will not be a primary factor.

I will still be using the very reliable AH3000 tiller pilot control head
but
since this unit is limit to only a couple amps output to the old linear
drive, I need to build a power controller circuit (not sure that the right
term), to deliver the full 14 amps to the new linear drive motor.

Both the old and the new linear drive was controlled by the switching of
polarity to the drive motor. I would use this same output from the control
head to switch the output polarity of the power controller..

First I would like to know which would be the most effiecent and reliable,
Transistors or Relays in this controller.?? I realize I could build it
from
regular, off the shelf automotive relays and if they fail, I can just plug
in a spare, but then if I mount my transistors in sockets, I could do the
same thing.

BTW. Either controller will be protected, below deck in a sealed box.

Can anyone offer a curcuit diagram for either transistor or the rely power
controller. I'm not an elex. whiz but I can build just about anything that
you guyz can sketch up for me. Or a good reference that might have such a
circuit.

Thanks,

Steve
s/v Good Intentions

Power Transister or Relays??

Steve
I can't help you with how to do it, but I feel your solution has to be
electronic, not relays. You are talking about switching up to 14 amps DC
perhaps 4 times per minute - that's about 40,000 cycles in a week of
continuous use. That's a number of duty cycles that would have one looking
carefully at specifications if it were an AC load. I don't think automotive
components will cut the mustard. No-one expects to start their car 10 times
per day, 365 days per year for 10 years!
So the solution has to be solid state; question is how you get it designed
and then prove it's reliability .....
Hope this helps.
David

"Doug Dotson" wrote in message
...
Steve,

I would use neither. MOSFETs would be my choice. Check out
International Rectifier's website.

Doug

"Steve" wrote in message
...
I finally located a stronger 12 volt linear drive unit for the tiller
pilot
on my 13 ton Ingrid 38. It has all the power and length of stroke that I
feel I need (when the going gets tough).

This unit has a 14" stroke (stop to stop) 1000# dynamic, 1500# static
and
overload clutch rated at 1200-1600# w/auto thermal overload.

However; the drive motors max current draw is 14 amps.. Now that sounds
like
a lot but under normal operating conditions it shouldn't take more than
5-6
amps and then only in pulses since the tiller load is normally fairly
light.
(from my observations of the AP performance recently, the duty cycle is
about 1sec on/15sec off. ) Under heavy conditions, I'm sure this will be
different and I have not data since the tiller load is too great for the
OEM
linear drive.

I will be using this AP set up mostly while motoring so power
consumption
will not be a primary factor.

I will still be using the very reliable AH3000 tiller pilot control head
but
since this unit is limit to only a couple amps output to the old linear
drive, I need to build a power controller circuit (not sure that the
right
term), to deliver the full 14 amps to the new linear drive motor.

Both the old and the new linear drive was controlled by the switching of
polarity to the drive motor. I would use this same output from the
control
head to switch the output polarity of the power controller..

First I would like to know which would be the most effiecent and
reliable,
Transistors or Relays in this controller.?? I realize I could build it
from
regular, off the shelf automotive relays and if they fail, I can just
plug
in a spare, but then if I mount my transistors in sockets, I could do
the
same thing.

BTW. Either controller will be protected, below deck in a sealed box.

Can anyone offer a curcuit diagram for either transistor or the rely
power
controller. I'm not an elex. whiz but I can build just about anything
that
you guyz can sketch up for me. Or a good reference that might have such
a
circuit.

Thanks,

Steve
s/v Good Intentions

Power Transister or Relays??

Larry W4CSC wrote:

Larry W4CSC

US Supports Apartheid! Vetoes UN resolution
condemning Apartheid Wall.
http://www.antiwar.com/hacohen/h052103.html
http://www.theage.com.au/articles/20...917478560.html
Can apartheid at home be far away?....
Apartheid NOW! Wall off Mississippi!

Well, Larry, I see you are still cloaking your hatred of Jews behind
support for the so-called Palestinians. Nothing much changes for you
except your meds, eh?

How sad.

--
__________________________________________________ __________
Email sent to will never reach me.

Power Transister or Relays??

Hmm....from the sound of an Autohelm, I was under the impression the
motor drive was a STEPPER motor, which varies with the number of
steps/second delivered from a digital drive. Listen to it run. It
doesn't cut on and off at all. Take it out into the waves and listen
to the FREQUENCY fed to the motor change from that low RPM,
intermittent bzzt,bzzt,bzzt that drives me crazy as it makes little
course corrections in calm waters, constantly, those little jerky
motions, to the full blown hardovers trying to keep up with the swells
offshore. It's not just turning on and off like your water pump.

As to the drive on a hydraulic ram, I believe it is driven from analog
electronics controlling motor speed, therefore hydraulic pressure. We
just installed a B&G Network Pilot with electro-hydraulic A unit on
Lionheart, an Amel Sharki 41 ketch. It looks like a perfect human is
piloting the helm...scary. If you go under the aft cabin bunk and
watch it work, you can hear the power to the drive motor vary as it
runs this way, stops, runs that way backwards. It doesn't come "on
and off" like a relay. To make small course corrections, it comes on
at a low level and power is applied gradually until the rudder
position sensor tells the electronics the rudder is, in fact, moving
slowly in the desired direction. At that point the motor stays at
that level of power until it approaches the correct course, then it
slows to a stop and reverses, bringing the helm, very gently, back to
center as the correction becomes reality. It's the smoothest
operating autopilot I've ever seen, and very quiet unless you're
sleeping on top of its motor.

If someone orders a 10 degree turn on the Pilot's controller, the
motor comes on hard to pull the helm over, but not to the stops. B&G
Pilot's manual says the computer "learns" the boat's handling
characteristics, constantly, and figures out how hard it needs to pull
over to make a nice, coordinated turn. As soon as the boat responds,
felt by B&G's fluxgate, the motor reverses very gently and pulls the
helm back to center....arriving uncannily AT center just as the new
course shows up on the display. Sure wish I could steer it by hand as
accurately as that...never oversteering, which is real easy to do on
the Amel's big rudder...(c;

I don't think any autopilot's control is an on-off simple
switch....Autohelm or hydraulic. Watch carefully when it's working.
It doesn't turn at a set speed on either.

Larry W4CSC

US Supports Apartheid! Vetoes UN resolution
condemning Apartheid Wall.
http://www.antiwar.com/hacohen/h052103.html
http://www.theage.com.au/articles/20...917478560.html
Can apartheid at home be far away?....
Apartheid NOW! Wall off Mississippi!

Power Transister or Relays??

I've had both the AH4000 wheel and this AH3000 tiller pilot apart and there
is no digital drive. Just a simple little 'weenie' motor and a set of
plastic reduction drive gears. (BTW the more recent, to 2000,
Autohelm/Ratheon APs still continued to use the same drive motors as the old
British Nautic and AH units.

I can put a meter on the motor leads from the control head and note the
switch of polarity from port to stbd.

The high freq. you maybe refering to could be from a pulse control to the
motor but from the circuit diagram of the control head, I can't see this as
'digital'.

You can download and look at the ciruit diagram on my web site..
http://hood.hctc.com/~esteve/private/manuals/ The document name is
AHcontrol head CCT1.doc

Steve
s/v Good Intentions

Power Transister or Relays??

Steve,

Assuming there is no ambiguity about the AP circuit. If you just need a
relay you can buy a solid state one already designed and packaged with
surge and arc circuitry built in. Google for electronic suppliers, they
shouldn't be hard to find.

Regards , Ron

Power Transister or Relays??

Massive SNIP

The controller circuit:
Here is a site I ran across. It is a run-down on FET H-Bridges for
FD/REV control of a DC motor. It presents a simple circuit, no special
FET driver chips. The down side is that you have to build (included in
article) a small device to provide 24v to operate the FETS.

Haven't tried it, but looks reasonable. Link below....

http://www.armory.com/~rstevew/Publi...Blanchard/nch-
brdg.htm

Woody

Power Transister or Relays??

"Steve" wrote in message
...
I finally located a stronger 12 volt linear drive unit for the tiller
pilot
on my 13 ton Ingrid 38. It has all the power and length of stroke that I
feel I need (when the going gets tough).

What make of linear drive did you go for then?

garry