Relays and servos

Control Boards, Controllers, Tethers, Ect.
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micoma
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Joined: May 14th, 2014, 4:16 pm
Location: Venezuela

Relays and servos

Post by micoma »

I want to build a simple ROV. I know enough about electronics to not hook the positive to the negative and to not mix voltage. That is about it. I intend to control my ROV with a joystick (3 thrusters) and on shore power. I have already figured out that running a power line to each thruster is just too much tether. So I am planning to use relays. Also I want to be able to tilt my camera. I have extensively read this forum so I know I need DPDT relays and I know how to wire them. But there many relays to choose. So please can someone just give me a link to the ONE I need to buy? Also am I correct that the relays need to be waterproof?

In order to tilt a camera I know I need a servo, pulling a string back and forth just won't work. I know that they have 3 wires - positive, negative, and a wire for some kind of signal. The signal is what I don't understand. How do you generate a signal if you are not using arduino or something like that? I have researched but haven't found anything that says how to make one work when it is just hooked to a battery. If someone knows another way to tilt a camera while it is inside a ROV please tell me. Thanks.
jpWA
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Re: Relays and servos

Post by jpWA »

If it isn't digital servo, the signal is usually just an analog signal from zero to whatever the max voltage for the circuit is. For some servos that the signal regulates speed instead of position, you could probably just turn them on and off with a relay wired to the signal port
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sthone
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Re: Relays and servos

Post by sthone »

It's hard to recommend a specific relay with out knowing your thrusters power consumption (amp draw), but as far as doing a tilting camera you can get away with just using a geared motor setup with forward/reverse control (same relay setup as thrusters) here are a few examples of how I have done it in the past.

Basic
http://www.homebuiltrovs.com/seafoxcamera.html

Little more advanced...
http://www.homebuiltrovs.com/seafoxretr ... lator.html

If you didn't want to mess around with making a gear setup it wouldn't be to hard to even take apart a servo and remove the electronics and just control the internal motor with a relay setup (or even just a switch) I've done this in the past with a tilt pan camera setup I made.

-Steve :sting:
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micoma
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Joined: May 14th, 2014, 4:16 pm
Location: Venezuela

Re: Relays and servos

Post by micoma »

I am going to use a Rule 1100 gph bilge pump for all my thrusters (3). Which relay do I need for those?

I am impressed with your fabrication. I was thinking that really all I needed was a really slow motor so when I hit the switch it won't jerk my camera back and forth. This is what I found - https://www.servocity.com/html/0_5_rpm_gear_motor.html. I might be able to hook the camera directly to the shaft so no need for a pivot point. I think it is slow enough that I should be able to tilt the camera in a controlled manner. I will use a relay for it also.

I though I would have to waterproof the motor but you run motors exposed. I have read other posts where people leave motors exposed. Are there certain types of motors that can run exposed and others not? How do you know when you can and when the motor needs waterproofed?
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sthone
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Re: Relays and servos

Post by sthone »

What Props do you plan on using?

That motor might be a little slow if I'm doing my math right at .5 RPM it would take about 30 Seconds to do a full 90 degree sweep. Which might not sound like a lot but it is.

Brushless motors usually don't have a problem running open in the water where as brushed motors will work but are more likely to fail or rust over time.

-Steve :sting:
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micoma
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Joined: May 14th, 2014, 4:16 pm
Location: Venezuela

Re: Relays and servos

Post by micoma »

You are right. They have a 1 RPM/minute motor also which is probably a better choice. I am going to use the 50 mm propellers. Still waiting on someone to point out the correct relay to use.
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