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31  Using Arduino / Audio / Re: Arduino DDS Sinewave Generator on: January 06, 2014, 10:13:59 am
You need to rename file ad9835_forum_arduino.ino to AD9835.h, and inside that file change #include "WProgram.h" to #include "Arduino.h".
32  Using Arduino / Project Guidance / Re: Controlling Turbocharger Solenoid With Arduino on: January 05, 2014, 06:40:54 pm
That's not a good choice of reed relay because the Arduino doesn't really have enough drive current for it. Look for one with a 5V coil and a coil resistance of at least 250 ohms. Here's an example: http://uk.mouser.com/ProductDetail/Hamlin/HE721A0500/?qs=sGAEpiMZZMukBJem%252bjLAJ4Cwn5GXgI1x. You don't need a series resistor with it, but it is advisable to use a small signal Schottky diode in parallel as a flyback diode, e.g. BAT85.

I've written about migrating from an Arduino to a bare chip here: http://miscsolutions.wordpress.com/2011/08/09/prototyping-small-embedded-projects-with-arduino/. If you program the chip via ICSP as I describe there, then you can program and reprogram the chip in-situ.
33  Using Arduino / Project Guidance / Re: Controlling Turbocharger Solenoid With Arduino on: January 03, 2014, 05:11:24 am
Why do you suggest against using a mosfet to send 14V to the wire? Can the mosfet not be constantly on for long periods of time?

It's a question of how to tap into that circuit in such a way as to minimise disturbance to the existing behaviour, including such considerations as what happens if the supply fuse fails. An alternative to the reed relay would be a p-channel mosfet, opto isolator, and a few other components to limit the mosfet gate-to-source voltage in the presence of transients.
34  Using Arduino / General Electronics / Re: Peristaltic pumps MOSFETs and diodes for auto dosing system on: January 03, 2014, 05:06:36 am
I think a 12V 1A supply may well be enough. The pump you originally linked to was 6V and specified 100mA no-load current. I doubt whether the current under a heavy load would be more than ten times that. And if you are using a 12V version of the same pump, the current should be halved.
35  Using Arduino / Project Guidance / Re: Controlling Turbocharger Solenoid With Arduino on: January 02, 2014, 04:53:44 am
I realize the voltage will drop during starting but I thought a high was considered over 2.5v on the digital pins so even with 10v applied it will still register a high. With the 33k it would allow 5.7v to the pin with 14v applied and isn't that too much and what if there are some small voltage spikes from the alternator?

You need at least 0.7 * Vcc to guarantee that the mcu will see a HIGH, so that's 3.5V on a 5V Arduino. The 47K series resistor is high enough to limit the current into the pin protection diode when the input is up to 50V.

Dc42 could you look at my earlier post with the diagram of the brake pedal switch and possibly answer those questions for me?

I don't see a wire labelled VT-WT. I advise against using a mosfet to tap into that, I suggest instead a 5V reed relay (which you can drive direct from an Arduino pin, just add a BAT43 or BAT85 flyback diode) connected in parallel with the switch.
36  Using Arduino / Project Guidance / Re: Controlling Turbocharger Solenoid With Arduino on: January 02, 2014, 04:16:44 am
btw the reason I suggested changing the 22K resistors to 33K is that the battery voltage will be much lower than 14V during starting.
37  Using Arduino / General Electronics / Re: Peristaltic pumps MOSFETs and diodes for auto dosing system on: January 02, 2014, 03:36:21 am
It looks to me that those pumps take less than 1A current, and you are not using a very high PWM frequency. So a 1N400x (for any x=1 thru 7) will be fine for the flyback diode.
38  Using Arduino / Project Guidance / Re: Controlling Turbocharger Solenoid With Arduino on: January 02, 2014, 03:32:04 am
1. Your "voltage divider" fed from S1 is not a voltage divider, it is a  22K pulldown resistor follows by a 47K series resistor. It will work, however it would be better to use a 47K resistor between the voltage source and the pin, and a 33K resistor from the pin to ground. Same for Vss and Ford PCM inputs if they are also 14V signals. The 47K is large enough to protect the inputs from at least 50V transients. If you want more protection than that, use 100K and 68K instead.

2. I would use 10K in series with the analog inputs, not 1K.

3. I would add a 100 ohm resistor in series with the mosfet gate.
39  Using Arduino / Project Guidance / Re: New project to automate a rotary drum filter for a fish pond on: January 01, 2014, 07:24:59 am
Personally I wouldn't use a relay, however If you only need to run the motor one way, then a mosfet + flyback diode will do the job for a lot less money than a motor shield.
40  Using Arduino / Project Guidance / Re: New project to automate a rotary drum filter for a fish pond on: January 01, 2014, 06:50:36 am
The first one is no good for your application, but the second one looks like a good choice to me.
41  Using Arduino / Project Guidance / Re: Protecting Arduino inputs from external inputs on: January 01, 2014, 04:47:20 am
I build lots of these testing modules if you will and on average I have to feed 0.94 volts for the Arduino to read 0.90 volts.  Some Arduinos require 0.94, some 0.95 and the highest I've had is 0.96 volts.  However going through the op amp I see I have to feed it 1.04 volts to for the Arduino to register 0.90 volts.   I know op amps can do scaling and its got me thinking am I inadvertently scaling the voltage without meaning to?  How do I correct this difference?  I need the Arduino to correctly read the voltage for my projects.

Your two main sources of error will be:

1. The analog reference voltage you are using. Don't use the default 5V reference if you will be powering the Arduino from USB or from an external 5V supply, because it will not be stable enough to provide a good reference. You can use the 3.3V pin as analog reference, which is more stable but will still vary a little between Arduinos. If the voltage you need to measure doesn't exceed 1V (or knowing "input above 1V" is sufficient when it does), then you can use the internal 1.1V reference, but again it will vary a little between Arduinos. I suggest you can store a calibration constant in the Arduino EEPROM.

2. The input offset voltage of the op amp. See its datasheet for how big this can be.
42  Using Arduino / Project Guidance / Re: New project to automate a rotary drum filter for a fish pond on: December 31, 2013, 04:33:47 pm
The standard Arduino motor shields use very old technology and are quite pathetic in their current handling capacity. Check whether the one you plan to use is adequate to drive your motor and solenoid before designing them in.

To adjust the set points, consider using a rotary encoder, with or without built-in push button.
43  Using Arduino / Project Guidance / Re: Arduino quadcopter pilot - electronics questions on: December 31, 2013, 12:20:20 pm
If you must do it yourself, here are some suggestions:

1. Run the Arduino at 3.7V, not 5V. You can't afford the weight of a boost converter. In fact, it if is a small quadcopter, it won't be able to carry the weight of a full Arduino board anyway. So prototype it on an Arduino, then migrate it to a bare-bones design when you have it all working.

2. TIP120s are rubbish for this application because of their saturation voltage. Instead, pick a small mosfet that needs only 3.5V gate voltage to switch it fully on. You must be building a small copter if you are not using ESCs, so you had better use SMD mosfets to keep the weight down. Maybe TSM2314CX.
44  Using Arduino / Project Guidance / Re: Usage of Arduino DUE for high speed data aquisition on: December 31, 2013, 12:11:46 pm
Even an ordinary 8-bit AVR Arduino could do that, it doesn't need a Due unless the analysis you speak of is very complex..
45  Using Arduino / Project Guidance / Re: Protecting Arduino inputs from external inputs on: December 31, 2013, 12:08:30 pm
Ahh didn't even know about that capacitor.  Will see what I can get added in there.  It's using the 5 volt power source from the Arduino.  I take it that's a noise supply?

Noise on the supply isn't the issue,the issue is that the op amp may be unstable without it. It's shown in Fig. 2 on the TI datasheet.
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