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Sequential Twin Turbo Controller

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VapidSquid

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Help! How can I make this happen:

Open gear motor driven valve when a light turns on, stop when valve is open, close when light turns off, stop when valve is closed.

Soooo, I'm a complete newb here and I'm hoping for some tech insight on the issue I'm attempting to solve. Currently I'm trying to figure out how to open a gear motor driven vavle and to stop it when its completely open. I plan on using my tac light signal to trigger it at any given rpm. However I'm sketchy on how to use the tac light turning off to brake the circuit and tell it to close when I drop below the set rpm. My primary issue at this point is getting the gear motor to stop when the valve is completely open/closed, otherwise I'll just burn out my little motor... I was thinking of using a similar set up to how simple security systems work, "brake the circuit alarm goes off..." In this case the tac light turning off would be the circuit braking?

Any and all help would be awesome, I'm a gear head and new to the world of electronics.

"Twin sequential turbo miata project"
 
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For one thing, turbo actuation isn't based off of RPM, it's based off of boost pressure, so you would want the larger turbo to switch over based on pressure, and not RPM. I'm assuming that's what you are trying to do.

You will need some kind of feedback switch to indicate when the valve is open and closed. I can't see any other way to make sure you don't burn out your motor or strip gear teeth. You could use current feedback to detect when the motor has stalled, but that's more advanced.

I can see this project being done with a microcontroller and sensors/drivers. It's probably possible to do it with less sophistication, but it's beyond my abilities to figure that out from a distance. It's not that "beginner" a project.
 
Turbines actually aren't controlled by the pressure, the waste gate be it internal or external keeps them from surging and overboosting. These are primarily controlled by boost/vacuum etc. The turbine itself will continue to spool until it reaches max rotation and then it will actually reverse direction and explode. In sequential twin turbo systems a valve is used to control gasses whech feed a secondary turbine, "the 2nd larger one," while the primary turbbine, "smaller one," spools in lower rpm. When the engine hits said volumetric point, ie, "3500 would be full boost off primary," the exhaust route is opened to the secondary turbine opening up to a full twin turbo. Using a power plate to cut the gasses from the secondary/control them was the simplest and most readily available item I could find. At the same time I could trigger it mechanically with an external waste gate actuator I would run in to leakage problems as well as over all fabrication issues, "I don't have the capabilities for the green casting process." With that said I do appreciate your time as well as your insight. Do you have any ideas as to how to stop the motor at a certain point other than programing a chip?
 
If you want to stop a DC electric motor quickly you can induce an electronic braking effect by switching in a load resistor across the motor, (Disconnect the supply first). If you want to stop it very quickly, the supply can be applied in reverse for a short time, (maybe through a low value resistor). The latter would require special consideration because the inertial loads could strip gears and/or damage the motor. (An H bridge configuration would be best for reversing the supply.

As Mark says, you will need sensors to determine open and closed positions with any method you use.

If the motor drive for the valve is fairly small, you might consider an R/C servo. (The type used in radio controlled cars and aircraft). These are proportional devices and have motor drive and position sensor incorporated. The input signal would be a pulse between 1mS and 2mS long every 20mS to give approx 90deg rotation of the servo ouput shaft.
 
Turbines actually aren't controlled by the pressure, the waste gate be it internal or external keeps them from surging and overboosting. These are primarily controlled by boost/vacuum etc.
What do you think Boost/Vacuum is? It's pressure. I am very well versed in turbo theory.

With that said I do appreciate your time as well as your insight. Do you have any ideas as to how to stop the motor at a certain point other than programing a chip?
Unfortunately, the only two ways I can think to stop the motor, I've already mentioned. A limit switch or current detection. A limit switch is obviously the simplist, but if you can't fit some limit indicator into the gear assembly or somewhere, then your out of luck. The only way I know how to use current detection is with a microcontroller and an ADC to measure it. The point of the current detection is that when the motor stalls, the amount of current it draws spikes way up. If you can detect this, you know that it's hit the stop. It's possible someone here who has much more understanding of analog electronics than I do might be able to help you out, with a non-microcontroller solution, but I'm sure the whole thing with the actuation all the way to the limiter and the logic to move it back again when the load is off, will be fairly complicated.
 
Thanks Guys!

Good stuff, and I appreciate all of your time and insight.
The parts are in, so now comes the fun bit!
 
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