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31  Development / Suggestions for the Arduino Project / Re: Love to see a recent sketches list on: March 26, 2012, 12:20:00 am
Me too! smiley +1
32  Using Arduino / Programming Questions / Re: Defining Board type on: March 19, 2012, 12:27:44 pm
Thanks for the replies.

I will use the comment idea. In this particular case I had been programming a Nano and then opened a Mega sketch and I was informed that A11 was undefined in this scope smiley-eek. It took a little head scratching to figure out what was wrong.
33  Using Arduino / Programming Questions / Defining Board type on: March 19, 2012, 11:35:27 am

Is there any way to define the board type in the sketch so I don't get surprising error messages when I switch between sketches designed for different boards but forget to choose the board type in the menu?

34  Using Arduino / Programming Questions / Re: INSTRUCTING ARDUINO TO RECALL A PREVIOUSLY GIVEN VALUE on: March 18, 2012, 03:49:04 pm
You seem to be confusing declaring (or creating) a variable with assigning a value (or changing) to a variable. If the variable is declared (i.e. int distance=0;) at the top of the code (outside setup() or loop()), its value can be assigned anywhere in the code (i.e. distance=55).

You need to create/declare the variable first (at the top) and then assign whatever value you want later e.g. distance=Serial.Read().
35  Using Arduino / Project Guidance / Re: DC dimmer circuit on: January 31, 2012, 12:39:40 pm
I have ordered the parts—they should be here in a few days.

I will use a heatsink, connect the 10k pulldown to the TC4429 input, and use a resistor value below 50 ohms in between the TC4429 and the mosfet.

In theory, if I did pull the gate of a p-channel mosfet to ground, would that not turn it on rather than off?

I am doing my best to grasp all of these details but sometimes my head hertz! smiley-grin

I will report back when the whole thing is installed.

Thanks everyone.
36  Using Arduino / Project Guidance / Re: DC dimmer circuit on: January 29, 2012, 05:09:06 pm
Thank you BenF and dc42! Your careful and clear explanations are very enlightening and helpful.

I need to keep the mosfet on the high side of the circuit. This is a retrofit, and I do not have access to the low side. I have a hefty heat sink that I pulled from a UPS on which I intend to mount the mosfet.

I have revised my diagram to reflect the changes suggested:
37  Using Arduino / Project Guidance / Re: DC dimmer circuit on: January 28, 2012, 03:06:22 pm
Your current design is guranteed to lock up and you may as well go back to the drawing board.

Well that shows how much I know! Transistors are still new territory for me.

dc42, thanks for the diagram. I found a IRF5210PbF which has a pulse current rating of -140A which is more than 15x my 8 amp steady current draw.

I have done some forum searching and this thread (,62503.0.html) recommends using a "TC4429" mosfet driver. It has something to do with the mosfet not switching cleanly with a transistor. Would this be better? What do you think?

I thought that a dimmer switch would be a piece of cake to set up. A perfect case of "famous last words".

38  Using Arduino / Project Guidance / Re: DC dimmer circuit on: January 28, 2012, 02:01:53 am
Secondly why use a IGBT?

Well I am not really sure why I chose that, maybe "ultrafast" in the name. Will it not work for this? (I already bought it.) smiley-red
39  Using Arduino / Project Guidance / DC dimmer circuit on: January 27, 2012, 09:04:42 pm
Hello all!

I am trying quickly to throw together a DC dimmer circuit for four two-amp bulbs in an automotive setting. I need to run the PWM at 30kHz to eliminate a horrible humming that these bulbs make. I have put together the following diagram showing all but the potentiometer that will be used as the human interface.

Could one of the experts review my circuit?

40  Using Arduino / Project Guidance / Re: Detecting Hot Melt Glue Level on: January 27, 2012, 04:44:13 pm
This system can't really be operated manually, it is impossible to see what is going on. The air pressure inside the system is released periodically (as the plunger descends) via a check valve.

I think I figured out the problem. Commercial premelt systems use capacitive sensing so it has to work (see attached).  My sensor wire was in electrical contact with the edge of the chamber so it was reading the capacitance of the container (which does not vary much) rather than the glue. smiley-red (It is kind of embarrassing, but sometimes you don't realise what is up until you begin discussing it.)

I did some tests and the glue does change the capacitance of the wire significantly so I think I can make this work after all.

I will let you know how it goes.

Thanks for the input.
41  Using Arduino / Project Guidance / Re: Detecting Hot Melt Glue Level on: January 27, 2012, 09:13:47 am
Hi Terry!

How much does the level physically change?

About three quarters of an inch.

Possibly ultrasonic ranger looking at surface from the top?

I am afraid the system is completely enclosed (see attached pictures).

What accuracy do you need? Or just high and low points?

Just high and low points. A solid block of glue sits on the grate and when the small chamber (5" diametre and 1" depth) under the grate is empty, the plunger needs to push down, then stop when the chamber is full.

42  Using Arduino / Project Guidance / Detecting Hot Melt Glue Level on: January 27, 2012, 02:00:31 am
Hello all,

I am trying to detect the level of some hot melt glue (250°F) in a premelt system I am making. I tried using a wire configured as a capacitive sensor but once it was coated with the glue, the value did not change even though the glue level dropped. I am not sure what to try next. Does anyone have any ideas?

43  Using Arduino / Sensors / Re: False triggering IR light gate on: January 27, 2012, 01:40:51 am
Yes, dc42, I changed the emitter to 5v.

The circuit is now working well!

A big thank you to Riddick and dc42!

If I could, I would buy you both beers! smiley-grin
44  Using Arduino / General Electronics / Re: Using an old computer atx power supply as a stepper power supply on: January 27, 2012, 01:35:57 am
Just because a PS can deliver up to 15A doesn't mean that 15A will be flowing, unless you have little enough resistance (high enough load) to actually draw that much.

That is right. To the OP, just remember that amperage is drawn (by a load) not pushed (by a power supply). Your PS can withstand up to 15 amps of power draw, anything less cannot be a problem.
45  Using Arduino / Sensors / Re: False triggering IR light gate on: January 25, 2012, 04:30:23 pm
Okay, here is the update.

Grounding the frame, using twisted-pair wires, and .01uF capacitors (to ground on the pin side) has resulted in 95% stability for the sensors. A huge improvement over my former 0% stability! smiley So I am very happy about that.

In the interest of gaining 100% stability I will try connecting a 1K pull-down resistor to ground on the pin side of the sensor.

I am very hopeful that this will work.

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