Do I want a motor shiled?

[Jarguess]

I need to read in a pwm signal and map it to a different pwm value to control two solenoids. I want it controlled by a switch so regarless of the pwm input, the solenoids will only be activated if the switch is activated. Additionally I need a third solenoid activated at 100% any time the other two are activated. Is the motor shield what I want?

Could I use a relay to activate more selonoids or would that cause to much delay for the fast switching?

Output needs to be in the 10-14 volt range and the input will either be 5 volts or in the 10-14 volt range (haven't decided on a sensor yet )

It seems to me that any of the product will do this simple task, but which will be the most efficent and cause the least amuont of delay?

[adafruit_support_bill]

The motor shield could control up to 4 solenoids - so long as they need less than 600mA. But I would use a MOSFET. One per solenoid plus a snubber diode will do it. MOSFETS are very fast and will switch up to 60A @ 30V.

[Jarguess]

If I wanted to use a schottky diode for a flyback what specs would you recommend? With the mosfet do I need to include a resister with the fly back to dissipate the current?

[adafruit_support_bill]

Diode specs would depend on the coil & the switching rate. In general, it doesn't hurt to overspec.
A diode in parallel with the coil should be sufficient.

[Jarguess]

I was thinking the flyback went between the mosfet and the controller, but you're saying it should go between my solenoid and the mosfet? I dont know much about the solenoid except that its 12volts and has a 9amp current draw. This will be used in a car so fugure ill be working with 14 or 14.5 volts. As for switching rate I was hoping every 10 milliseconds. Is that possible? If not what kind of resolution can I expect, 20 milliseconds?

[adafruit_support_bill]

but you're saying it should go between my solenoid and the mosfet?

No, The flyback is in parallel with the coil. The following diagram is for a relay, but driving a solenoid is the same:
http://www.arduino.cc/playground/uploads/Main/relays.pdf

9A is a fairly hefty coil. When you say switching every 10 ms, do you mean a 10 ms PWM period (100 Hz) to maintain the solenoid position or are you actually trying to actuate the solenoid at that rate?

The MOSFET is capable of switching much faster than that. But your solenoid actuation rate will be limited by the inductance of the coil.

[Jarguess]

OK sorry, I'm a seasoned professional programmer but the electronics is new to me.

In the diagram TI102 is the mosfet and 1N4004 is the power diode being used as a flyback in parallel with the relay coil or in my case the solenoid. If I'm using the Arduino with the motor shield and usign the T0-220 mosfet, what vlaue do I need for R1

Drawing1.png (7.87 KiB) Viewed 1085 times

is this correct then?

When you say switching every 10 ms, do you mean a 10 ms PWM period (100 Hz) to maintain the solenoid position or are you actually trying to actuate the solenoid at that rate?

Actually trying to actuate the solenoid at this rate. The solenoid manufacturer at one time sold a progressive controller for the solenoid. The factory controller could start the solenoid at 10% rate and ramp to any percentage desired in 1% steps so I'm assuming the solenoid can do it. What I'm thinking is at 1% you have 10ms on and 990ms off, at 50% 500ms on and 500ms off, or 31% 310ms on and 690ms off.

Does what I'm trying to do make sense or am I doing this all wrong?

[adafruit_support_bill]

If I'm using the Arduino with the motor shield and usign the T0-220 mosfet, what vlaue do I need for R1

You don't need the motor shield or the resistor. You can drive these MOSFETs directly from a digital pin on the Arduino.

Actually trying to actuate the solenoid at this rate. The solenoid manufacturer at one time sold a progressive controller for the solenoid. The factory controller could start the solenoid at 10% rate and ramp to any percentage desired in 1% steps so I'm assuming the solenoid can do it. What I'm thinking is at 1% you have 10ms on and 990ms off, at 50% 500ms on and 500ms off, or 31% 310ms on and 690ms off.

What exactly are you trying to do with this solenoid? Do you have a link to a spec for it?

From your description, it sounds like the factory controller is designed to control the force on the solenoid via PWM, not to have it go back & forth at 100 Hz. Solenoids are power-hungry devices that require a lot of energy to actuate, but less to maintain their position. It is common to apply 100% at the start to actuate, then back off to whatever level is needed to maintain the position.

[Jarguess]

Haha

What I'm trying to do is build a nitrous controller. The programmable controllers available are extremely expensive. Most of the controllers on the market bring the nitrous gas flow on at around 10-20% flow and then over a pre designated time progressively increase the gas flow up to 100%

I want to be able to control the gas flow based on my own map related to rpm. This way I can bring up the gas flow on a curve instead of linearly. I also want to control the gas and nitrous solenoids individually so I can control the fuel mixture. My goal is to control the gas flow relative to the power band and/or timing curve of my engine.

I was using the motor shield because I want to control 4 different solenoids independently (two stages of nitrous), plus another one or two additional saftey solenoids (always 100% flow).

I don’t have any specs, however I just looked at the instruction sheet for their programmable controller (http://holley.com/data/Products/Technical/A5164-SNOSrev.pdf) and it says

Setting the NOS Pulse Frequency
Place the Select Switch at the NOS Pulse Frequency position. Using the .001 Data Switch, select the desired frequency.
Example: [0 = 20, 1 = 25, 2 = 30, 3 = 35, 4 = 40]
Press the Programming Switch to enter your selection.
NOTE: The Pulse Frequency = how many times per second the solenoids operate. The higher the frequency, the more pulses per second. All production NOS solenoids operate best at 25 – 30 Hz.

I guess you’re right; I need control the force on the solenoid via PWM. How do I do that?

[Jarguess]

NOS solenoid http://holley.com/16020NOS.asp
Fuel solenoid http://holley.com/16080NOS.asp

This is basicly what I want, but I want to use the Arduino so I can program a map for each solenoid based on a single pwm input and activation switch. http://www.ti.com/lit/ds/symlink/drv101.pdf

[adafruit_support_bill]

All production NOS solenoids operate best at 25 – 30 Hz.

The specs don't give any detail about the electrical characteristics of the solenoid coil, but you probably should stick close to that recommendation. Solenoid coils are inductors and their response changes with frequency.

[Jarguess]

So how do I control the flow without changing the frequency?

[adafruit_support_bill]

Generally it is done by controlling the duty cycle. Your basic frequency is 25-20Hz, but the coil is energized for somewhere between 0% & 100% of that time.

[Jarguess]

So lets assume im running someplace between 29-30 hertz. If my duty cycle is 3% then my signal is on for 1 millisecond and off for 33. If I want a 60% duty cycle my signal will be on for 20 milliseconds and off for 14. And my best resolution is basicly 34 steps or 3% blocks. Is that right? So the electronics are the same, just my programming is different, correct?

[adafruit_support_bill]

And my best resolution is basicly 34 steps or 3% blocks.

Only if you restrict your timing to 1ms units. You can get much finer than that. This page is a good resource for PWM information: http://arduino.cc/en/Tutorial/SecretsOfArduinoPWM