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1  Products / Arduino Due / Re: Do I need to use the Due Scheduler library? on: April 30, 2013, 10:27:22 pm
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During this 6ms I am using pulseIn to count how long a pin is HIGH, so the CPU is blocked (I believe so).

You could use an interrupt to trigger when the pin goes low, and then check the value of millis() if you need to know how long the pin was high.
2  Using Arduino / Sensors / Re: Can anyone identify this? on: April 15, 2013, 06:01:28 pm
A BJT, thank you Magic!

(I must have transposed some of the numbers, Google wasn't working for me...it was late, I was tired!)

3  Using Arduino / Sensors / Can anyone identify this? on: April 15, 2013, 12:29:20 am
I pulled this from an old G5, I am pretty sure it is a temperature sensor. It is a TO-92 package. I couldn't recognise the symbol.

Can anyone identify this?

THX!
4  Community / Exhibition / Gallery / Re: AC Light Dimming [success] on: September 25, 2012, 01:11:40 pm
FYI, this AC SSR can be controlled with variable DC input (PWM):

http://www.alliedelec.com/images/products/datasheets/bm/CRYDOM_CO/70130557.pdf
5  Community / Bar Sport / Re: Aluminium tube on: September 25, 2012, 12:49:59 pm
Thanks kf2qd. I already got my DOM steel tube, but I will bear that in mind for future needs. The length was about 9 inches.
6  Community / Bar Sport / Re: Aluminium tube on: September 20, 2012, 01:03:57 pm
Yes that could work too! Thank you.
7  Community / Bar Sport / Re: Aluminium tube on: September 17, 2012, 01:12:56 pm
Well I searched for hours yesterday, but to my surprise, I could not find ANY 0.75" OD tube with less than 0.5" ID!

This is for a hot-melt (250°F) glue nozzle. I wanted Al for its thermal conductive properties. I even considered brass, but I could only find sources the right size in India and China.

I finally ordered a DOM tube from onlinemetals.com this morning. I can live with a slower warm-up time, it is just not ideal.

Thanks for the help though!
8  Community / Bar Sport / Aluminium tube on: September 16, 2012, 12:58:09 am
Does any know where I can find (online, preferably North American continent) an aluminium tube with an OD of 0.75" an ID of 0.44" or less and a diameter tolerance of .005 or less?  smiley-roll

TNX
9  Using Arduino / Project Guidance / Re: 5v Motor from 12v with pwm on: August 06, 2012, 06:38:19 pm
Hmm, well I was hoping for a better consensus...  smiley-grin

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PWM turns on and off the supply voltage (12V) frequently. It doesn't change the voltage. The motor will still see 12V when it sees any power.

That was my fear, however, a mulitmeter does read the pwm output as half voltage.

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Motor reacts on RMS value, as any inertial system (including heaters).

And that was my hope, that the peak would be quick enough that it wouldn't have time to cause damage.

Anyone else?
10  Using Arduino / Project Guidance / 5v Motor from 12v with pwm on: August 06, 2012, 01:45:43 pm
Hello everyone,

Can I run a 5v motor from a 12v power source if I use a PWM (500Hz) duty cycle that does not exceed 50%?

TIA
11  Using Arduino / Project Guidance / Re: DC dimmer circuit on: August 04, 2012, 03:54:32 pm
Phew! It is finally working!

Thank you dc42, for patiently putting up with me!

I added:
A secondary mosfet in parallel (unrelated to the problem) to distribute the amperage draw,
two decoupling capacitors (100μF and 1μF) to the source of the mosfets,
a reverse protection diode to the power input for the whole circuit,
a 1k resistor between the Arduino output and the TC4429 input,
and I reduced the pwm to 25kHz just in case.

It works beautifully!

THANK YOU once again!
12  Using Arduino / Project Guidance / Re: DC dimmer circuit on: July 21, 2012, 02:59:54 pm
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No, it should be much closer to the mosfet source and the ground side of the LED than that, so that the switching transients don't propagate to the rest of the circuit. I would use 1uF ceramic in parallel with at least 100uF electrolytic.

I see, (I assume "the LED" refers to the 8 amps of DC lighting) I will do that.

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However, this doesn't explain how you managed to damage a TC4429 when there was no load connected - that puzzles me.

Does that suggest the power supply disconnection causing transients then? If you are puzzled by this, imagine how I must feel!

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I suggest connecting a resistor of about 220 or 470 ohms between the Arduino output pin and the TC4429 input.

I will certainly do that.

Thank you!
13  Using Arduino / Project Guidance / Re: DC dimmer circuit on: July 21, 2012, 01:40:40 pm
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It's a TC4429 - makes a difference.

Well I got the numbers switched and then kept copying it. smiley-confuse

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You'll probably be terribly insulted, that I'm trashing your creation, and that's wholly not my intention, but I take particular issue with your grounding in addition to other aspects of your wiring and construction technique.

I'm not insulted. I am still very much a beginner. I know the circuit isn't pretty but I do make sure all the solder connections are very strong. I am grateful for any criticism.

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1. I can't see any wires connected to the drain terminal of the mosfet in your photo. Was the load actually connected during your testing? If so, how was it connected (in particular, where was it connected to the ground line), and how much current does the load take?

There was no load during my most recent test.

In a previous test, with the first TC4429 that I burned, it was connected to the 8 amp lighting. The ground lead on the board was connected to the vehicle ground. I do not know exactly where the ground wires go inside the vehicle, but I do get good continuity between my point of connection and the lighting ground.

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2. What is the value of the decoupling capacitor connected between the supply and ground pins of the TC4429?

1 μF, 50v.

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3. What is the nature of the 12V power supply, and what is its off-load voltage? I'm wondering whether it produces a temporary voltage reversal during startup or shutdown, or alternatively that it produces a lot more than 12V when the load is not energised. Assuming you didn't short the output of the TC4429, there must be something nasty happening on the supply pins to cause it to fail, and this would likely cause any other driver chip to fail too. The Arduino is protected to some extent by the diode you put in series with the Vin pin.

My testing power supply is a switching transformer. It outputs a constant 11.9v, with or without load (load being the Arduino in this case, it is not powerful enough to power the lights). I do not have any reverse voltage protection between the power in and the TC4429, and after sleeping on it, I am thinking that may be the problem. It was working for a while with the 32KHz PWM. When I came back the next day and powered it up it had failed. So maybe it is something to do with power cycling.

In the vehicle, where the first TC4429 failed, the power is just a 13.8v lead.

Any switch can cause reverse transients can it not? I just didn't think of that before.

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4. Why are you using a switching frequency as high as 32KHz? The higher the switching frequency, the more careful you need to be with circuit layout, to keep the inductance of critical paths low.

To eliminate a disturbing hum which these lights make when pulsed. I had the dimmer working before with an IPS6021 high-side switch (I really like them), but they have a maximum frequency of 1.5KHz. At that frequency the lights sound like a horde of mosquitoes.

I have calmed down since yesterday's bitter disappointment.I will order a couple more TC4429s (maybe I should get a reel!) and put reverse protection diodes on the voltage inputs.

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To avoid such transients, add a decoupling capacitor between the -ve side of the LED and the source of the mosfet.

Between pins 1 and 8 of the TC4429, correct?

Any other suggestions would be very much appreciated. I really do not want to take any more chances, I have learned my lesson. smiley-red

Thanks very much.
14  Using Arduino / Project Guidance / Re: DC dimmer circuit on: July 20, 2012, 05:54:24 pm
How about using a motor driver such as an SN754410?

Or a TI UC2714?

My opinion of the TC2249 is at an ultimate low. I am not sure I want to order more...although its failure is probably a result of my inexperience.

Thank you for your help, dc42.
15  Using Arduino / Project Guidance / Re: DC dimmer circuit on: July 20, 2012, 04:06:04 pm
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What value resistor do you have between the TC2249 output and the mosfet gate?

47 ohms.
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