Looking for custom servo design (Paid)

[nhtshot]

I'm in the Chicago area and looking for someone to do some servo controller design for me. This is a paid contract.

If you have experience with motor controllers and feedback systems, I really want to talk to you.

[Alex]

[mod note: moved to proper forum]

[Addidis]

A little more info would be nice. What kind of mcu are you wishing to use. How complicated is the work to be done. what kind of interface are you looking for (serial usb none*just program the mcu to update) I have some experience with servos. Not the best not the worst.

If you are willing to use a basic stamp for your project, I would recommend rather then paying some one for their time , buy a "what is a microcontroller" kit from parallax. It cost 99 bucks at radioshack and will teach you to write the code (in basic eww) and provide a servo and serial interface board for you to learn to write this code your self. The basic idea will be easy to pick up in this manner IF your project allows for it. Its not the path to go if your looking for more then a one off project as Basic stamps cost a whole bunch by them selves. But the ability to program in basic and the nice book it comes with is effective to learn.

[badcommandorfilename]

I'd like to help you - I know a lot about Real Time Control systems, and this sounds like an interesting project.

Unfortunately, I'm nowhere near Chicago so I doubt we would ever be able to meet in person. If you don't mind a long distance working relationship, PM me and I'll see what I can do.

[jes1510]

Please, for the sake of the industry do not under any circumstances use a basic stamp in a commercial product.

[Addidis]

agreed.

I Just prefer teaching to subcontracting. Really there is not enough information given to make a proper assumption of his intents

[nhtshot]

I made a vague post at first because I've never been to this forum before and I wasn't sure how they look upon posts like this. Since the powers that be don't seem to mind, and were nice enough to put my thread in the right spot, I'll give some more details.

This is not a robotics project per se. The 10 mile view is that we're building a custom multi-fuel ECU for a generator. It's based on a freescale cpu:

http://www.freescale.com/webapp/sps/...8A25802570256D

We can buy the interface off the shelf for the fuel injectors and the ignition module. The one interface that we can't buy off the shelf is to an electronic throttle body. I was able to get a schematic for the part we're using and it's basically a servo without a control board. Inside the unit is a motor and two pots. It doesn't have any of the logic usually found in a servo though.

So, what I need is someone to design a circuit to make this throttle body work more like a standard R/C servo. I want to pass it a single input signal and have it move to the proper position, read it's own pots for feedback and not give me any trouble about it.

If you're interested, drop me an email at nhtshot@gmail.com and I'll give you the precise details of the throttle body in question.

[nhtshot]

A couple quick points of clarification:

I'm not trying to build a throttle body or a controller board to run standard (r/c type) servos.

I have a throttle body bought that has the motor and potentiometers built in to it. It does not have any control logic. The pin connector has pins for the motor leads and the pots and no circuitry of any sort on the inside. I don't need help interfacing to a standard servo, I can do that. What I need is to turn a throttle body that does not have any circuitry inside it into a standard servo.

I've already found several designs for home-built servos, but they are not really intended for use in this kind of an application. The two issues that prevent any of the circuits I've found from working are as follows:

1. The throttle butterfly is on a spring. The motor, therefore, has to always be pushing to keep the valve open. This requires a very substantial amount of current that will be flowing constantly. I also have almost no tolerance for failures. The design and parts have to be able to output the needed amperage at 25-30% duty cycle so they'll have a long lifetime.

2. I cannot change the wiring or values of the pots. There are two pots inside the off the shelf throttle body that I cannot change. They are attached in opposing directions and are at 500-1.2k. I'm not familiar enough with voltage dividers, etc... to get the values on the feedback loop correct. Furthermore, since these parts are built into the unit, I have to be VERY careful in experimenting. I cannot replace them if I fry one.

So, I'm looking for someone that has enough knowledge about these kind of circuits to come up with a design that meets the above requirements with a minimum of experimenting on the actual equipment. I don't care about the interface to the micro controller. Right now, I'd be happy to just be able to drive the position of the throttle body with a pot.

I do appreciate all of the responses, but I don't think that I was very clear on exactly what I'm trying to accomplish.

[zoomkat]

Can you remove the throttle body spring? If you are controlling the throttle body with a servo, then no need for the spring. You may want to look at "drive by wire" throttle bodys that don't use mechanical linkages for operation and control. I got involved with fuel injection when the mass air flow monitor on my truck started going bad and eventually had to be replaced with a new throttle body (on a Nissan the throttle bodys appear to be calibrated to the monitor module by maching the bottom of the throttle body). A most interesting exercise in how things work.

[nhtshot]

No, it's basically a solid unit. I suppose it would be theoretically possible to change out some of the innards, but it's built pretty well and I'd rather not mess with it. Besides, the spring is intended as a fail-safe if there's an issue with the electronics. Run away Toyotas anyone? Perhaps they should have used the German design (the throttle body I'm working with is a VW part).

The part I'm using IS a "drive by wire" throttle body. Instead of mechanical linkages, it has an electric motor and some pots attached directly to the valve. It does not have any servo logic inside of it. The connector on it has pins for the motor and pins for the pots, that's it. I have to implement all of the servo logic outside the unit. That's what I'm here hoping to accomplish.

Unfortunately, while there's a wealth of information about interfacing with servos, there's next to nothing on building them from scratch. There are some bits and pieces out there and I've done quite a bit of experimenting, but it's obvious to me that it will take a long time for me to make this work by myself, which is why I'm here looking for expert help.