Servo driver?

[Tim_Duggan]

Hi guys,

I have a requirement for something that can switch a normal servo to two different set positions based on a resistance value input like a pot, and independent of a receiver (so essentially not r/c).

Does anyone know if any such device exists, or have a schematic or plans to build something that will do the job?

Thanks in advance,

Tim

 

[Tim_Duggan]

Hi Greg,

A quick Google search found schematics to have a servo travel to a point A or B, dependent on a microswitch input. (it's the one for retract doors on a scale P51)

It could probably be tweaked. What I need to figure out is what would be the best way to make it switch between the two positions based on a resistance value from a thermistor. It's probably simple, but I'm not in the right frame of mind at the moment & I want to keep it all miniature and running on 5 - 6VDC, preferrably low current draw.

Cheers,

Tim

 

[Don Brown]

The answer is yes.

There is a cheep reliable PLC board (programmable logic control) on the market that will directly drive servos (buy on-line for less than $20 US). It can be programmed from any computer with a USB port (with free software) and once programmed it will operate as a stand alone device.

I am working on a digital starting clock that uses this board. I have it working on a breadboard but haven’t built the full sized version yet. The finished clock will draw less than 1.5 amps and operate on any cordless drill battery from 12 to 24 volts.

Check out http://www.arduino.cc/ for more info.

DonB

 

[Tim_Duggan]

Thanks Don,

I have heard of Arduino's and seen that they support our servo's. Thinking it might be a bit overkill for this application to use logic, but given that it's become so cheap and the code seems to be shared about, it may be something I need to think about.

Thanks,

Tim

 

[Don Brown]

Another thought. Do you have access a 2.4 radio system from a Miss Vegas that is not being used? Mod the transmitter to get it to do what you need.

DonB

 

[RodneyPierce]

Tim, whats up your sleeve now brother?

 

[dwilfong]

The answer is yes.

There is a cheep reliable PLC board (programmable logic control) on the market that will directly drive servos (buy on-line for less than $20 US). It can be programmed from any computer with a USB port (with free software) and once programmed it will operate as a stand alone device.

I am working on a digital starting clock that uses this board. I have it working on a breadboard but haven’t built the full sized version yet. The finished clock will draw less than 1.5 amps and operate on any cordless drill battery from 12 to 24 volts.

Check out http://www.arduino.cc/ for more info.

DonB

This is some great info. This is what I have bin looking for to build a eng control system.

EGT- needle control and head temp- water control all in one.

David

 

[hugh hargett]

PLC's are way more elaborate than what you need. I basic stamp 2 module would be more reasonable for such task. Most plc's have over 100 i/o's you only need 2; just so you understand how overkill that would be. programming a plc requires some knowledge of either code or graphic text editing where you draw out the gates look at the ouputs then copy the code into the plc. Also most Cpld' boards(altera) etc are much larger than anything wed use in a boat. id just but a servo testor from HK thats the easiest route if youre no programmer. If you insist you can fine code and schematic for either analog or digital based circuit. Analog is possible so no mcu but analog design is harder to grasp and harder to analyze from a signals prospective. TTL is hi and lo 1 and zero.

PLC's(allen bradleys) are used to run automated factory lines nuclear plants and the such not to mention the virus thats floating around to attack plc's the same one that destroyed the radioactive spinners in IRAQ can now be directed to attack plc's anywhere . Its gonna be I robot real soon. Stuff will just start doing its own thing controlled via internet by some radical fool.Plc's also mount on the wall and are big. The anlog interface alone is bigger than a 6slipo pack the controllers is a big as your boat. A cpld is probably what was being suggested but even they are way overkill.The adruno unit is nice but if thats your only task it will be a waste of the adrunos power it can do alot more than run a pot based servo.

Pm me if you need a few schematics but again save yourself the trouble of reinventing the wheel and buy a servo tester hack it and put it where you want it.

If you get a basic stamp ill give you the sample code for a pot driven servo.

Hugh

 

[hugh hargett]

The answer is yes.

There is a cheep reliable PLC board (programmable logic control) on the market that will directly drive servos (buy on-line for less than $20 US). It can be programmed from any computer with a USB port (with free software) and once programmed it will operate as a stand alone device.

I am working on a digital starting clock that uses this board. I have it working on a breadboard but haven’t built the full sized version yet. The finished clock will draw less than 1.5 amps and operate on any cordless drill battery from 12 to 24 volts.

Check out http://www.arduino.cc/ for more info.

DonB

Be careful with your clock as I started mine then realized the guys never told me anything about the rules as they apply to the clocks ( digit height etc.) :huh: so I had to go back and revise my entire circuit to meet the rules but ill pm you some photos of my clock.

 

[Tim_Duggan]

Another thought. Do you have access a 2.4 radio system from a Miss Vegas that is not being used? Mod the transmitter to get it to do what you need.

DonB

Hi Don,

No but am running a 4PKS and have a spare channel. I want it completely independent and automated though.

Looking at the size of the Arduino it's too big to fit and the weight penalty may excede the benefit.

 

[Tim_Duggan]

Tim, whats up your sleeve now brother?

Just an idea I've had in my brain for years, that someone else just re-kindled with their own experience.

 

[Tim_Duggan]

name='dwilfong' timestamp='1332273748' post='464024']
This is some great info. This is what I have bin looking for to build a eng control system.

EGT- needle control and head temp- water control all in one.

David

Bingo. I'm thinking smaller steps to begin with - proof of concept on one part. Make it work with temp, then move on to the others. Add on-board glow at partial throttle in too.

 

[Tim_Duggan]

Pm me if you need a few schematics but again save yourself the trouble of reinventing the wheel and buy a servo tester hack it and put it where you want it.

I think this could have potential but am not familiar with the servo tester. The only thing is I don't want proportional movement of the servo, just a point A and a point B. So when the resistance value of the thermistor reaches a certain value, the servo switches from point A to point B at maximum servo speed, and vice versa.

 

[dwilfong]

I was messing with Tommy Dodd on a system then he disapered with out a trace.

If trying it on a .21 boat weight would be of the most importaince. On larger boats not so much.

Have a Perry control valve I have messed with to control the water. But this needs a seperate servo to run it.

this looks promising for the larger boats.

http://www.kpiwebsite.com/products-MPV.html Can order with different orifices and control voltages.

As far as the fuel put the needle right on the carb to get instant reaction.

Have the Eagle tree thermal coupler add on card to monitor two sensors. Drill a hole in the button and silver epox it in place.

Many options with a small PLC. the smallest one with the UBS interface looks good. http://arduino.cc/en/Main/ArduinoBoardNano

It is no larger than the Eagle tree V4.

Gust what i need a new project.

David

 

[hugh hargett]

Pm me if you need a few schematics but again save yourself the trouble of reinventing the wheel and buy a servo tester hack it and put it where you want it.

I think this could have potential but am not familiar with the servo tester. The only thing is I don't want proportional movement of the servo, just a point A and a point B. So when the resistance value of the thermistor reaches a certain value, the servo switches from point A to point B at maximum servo speed, and vice versa.

tim i may be able to dig up an actual circuit me and friend built almost 20 years ago. i used it to impliment motorization in an car stereo install. Full analog. Set the end points with pots throw a switch one way it goes that way switch it the other way it goes to the enpoint in the opposite direction.

Point to point wiring looked like spaghetti but it worked.

by the way the adriuno nano unit is only the size of a 40 pin pic chip

 

[Tim_Duggan]

That could work Hugh, just needs some sort of trigger based on thermistor input rather than a switch.

 

[Craig Murphy]

Tim,

As per David's post http://arduino.cc/en...rduinoBoardNano would probarly suit, I have a full Arduino kit if you want to play with it for few weeks. Been using it to experiment with some similar ideas.

 

[dwilfong]

Well here is the next step what is the ideal head temp and ex gas temp?

Will be great to be able to control each but what is the mark. will it change with oil and nitro content? will all eng be the same?

Dose a small eng need more than a large eng?

Lets see what you all think.

Would be great to get a kit setup to get it out there for testing. One person only has so much time to test.

The more sharing info the sooner it will come together for all.

David

 

[Charles Perdue]

There are many types and sizes of the Ardunios. Spark fun has a mini and a micro size avaliable. The micro is not much bigger than a quarter and it will do what you want. It cost less than $20.00. Do not let someone scare you away from being creative. The first couple of times that you play with them, they seem to be complicated, but they really are not. There is a lot of instructions on the Spark Fun site and as much help as you could ever possibly need.

Enjoy,

Charles

 

[hugh hargett]

Tim youre not scared are you? lol PM me if you need some help.