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1  Using Arduino / Project Guidance / Re: Dealing with servos & physical resonance on: July 02, 2012, 01:24:07 pm
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maybe the torque-ratings are too low for the loads

Maybe, that's what I thought at first, but if I push them firmly with my finger while powered they stay put so I figure they should be powerful enough. I'll see if I can get a video up tomorrow.
2  Using Arduino / Project Guidance / Re: Dealing with servos & physical resonance on: July 02, 2012, 01:05:26 pm
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The rods appear to be too thin and wiggly

The one I was referring to was cut from an Animal-grade professional drum stick.

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you could 'park' the servo by detaching it

Good idea, I'm not sure it would be feasible the way my project works (I have around 8 servos, attaching an detaching them in succession seems like a mess waiting to happen) but I'll give it a try.
3  Using Arduino / Project Guidance / Re: Dealing with servos & physical resonance on: July 02, 2012, 12:25:19 pm
Actually, even moving one of my servos from a position where it's resting to a (position + 1 degree) makes it enter self-oscillation, so a software solution seems impossible.
4  Using Arduino / Project Guidance / Re: Dealing with servos & physical resonance on: July 02, 2012, 10:44:41 am
Thank you @oric_dan & @PeterH, great suggestions. I'll see if I can get by using software (i.e. deceleration just near the final position). I'll write back here if I achieve something useful. I like the paddles idea, too :)
5  Using Arduino / Project Guidance / Re: Dealing with servos & physical resonance on: July 02, 2012, 09:42:15 am
Thanks but that's the opposite of what I'm trying to achieve (I need the fastest possible movement).
6  Using Arduino / Project Guidance / Dealing with servos & physical resonance on: July 02, 2012, 09:22:07 am
Hello,

I've been playing around recently with servos which move long, thin wooden rods (around 30cm long and 8mm is diameter). Each rod is attached in one extremity to the servo (think of it like a large needle). When the servo is commanded to go to a position, depending on the rod size and weight, there is significant resonant feedback on the rod, which oscillates back and forth very loudly around the position it has just reached. It has to be stopped by touching it, otherwise it can rattle for entire minutes.

I can find a mechanical solution to it (using absorption pads, similar to what goes on inside a piano), but this restricts the movement arc. I tried to find a solution in software, by sending out slight variations in position (in a direction opposite the movement direction) after different short intervals (10 to 200 milliseconds), but this doesn't help.

If anyone has any ideas on how to limit this oscillation, I'd be very thankful.
7  Using Arduino / General Electronics / Re: Help with troubleshooting a circuit error on: July 02, 2012, 08:17:01 am
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ALWAYS include power supply decoupling capacitors

I will, thank you. However, the problem I had is my candidate for the Stupid Oversight of the Day contest: Arduino's ground and the circuit's ground should eventually meet somewhere, of course...

Thanks a lot for all your suggestions, you made me look yet again at what I thought was properly wired :)
8  Using Arduino / General Electronics / Re: Help with troubleshooting a circuit error on: July 02, 2012, 07:03:20 am
Sorry, that was left out of the schematic. Pins 11 & 12 are of course connected to the Uno, 10 to 5V and 13 to GND (just like the first 595). The only pin not connected to anything is the serial out pin of the second 595 (pin #9).
9  Using Arduino / General Electronics / Re: Help with troubleshooting a circuit error on: July 02, 2012, 06:48:32 am
Not yet, since the whole thing isn't connected to the servos it's supposed to operate (and that's the reason I was told to add those capacitors). But anyway, the breadboard circuit work without them, so I'm thinking it must be something else.
10  Using Arduino / General Electronics / Help with troubleshooting a circuit error on: July 02, 2012, 05:23:13 am
Hello,

I have a problem with a circuit I just built (cf. attached schematic). In works perfectly well on the breadboard. The *perfboard* version, with everything soldered on, has a small issue which I don't understand.

The Arduino sketch mainly lights up different LEDs with the HC595s according to button presses shifted in through the HC165s (it's a complicated menu system for a device). This functionality is preserved entirely in the perfboard version, i.e. I can select buttons and LEDs display like they should.

The one notable exception is the top right button: when it's pressed, the button pressed is registered by the sketch but all the board LEDs start blinking quickly at a very dim level. If, say, a LED somewhere in the middle is set to be ON (normally getting 1.8V), then the LEDs to the left of it are dimmer than the ones to the right of it, and the LED itself is now getting only 1.2V (i.e. the HC595 seems to be sending it, and it only, 0.6V less than it should). This behavior only lasts as long as the button is held.

I've checked the sketch several times, outputting variables to the Serial Monitor, and it's not a software issue. I've also replugged everything back to the breadboard version and the problems disappeared. I've examined several times the perfboard version but I can't figure out what could be causing the problem.

Is there any way someone could help me figure this out?

Thank you.
11  Using Arduino / General Electronics / Re: Difference between CD74HC165E & 74HC165N on: June 29, 2012, 04:30:42 am
Thank you!
12  Using Arduino / General Electronics / Difference between CD74HC165E & 74HC165N on: June 29, 2012, 04:11:21 am
Hi,

I bought, without looking closely, three CD74HC165E ICs and one Philips 74HC165N. Every datasheet I find on the Philips one doesn't mention anything about the "N" variety. Both chips are 16-pin PDIP. Does anyone know if it's same to assume the Philips one will behave exactly the same as the other three?

Thanks a lot.
13  Using Arduino / Programming Questions / Re: Using a Timer interrupt with the Servo library on: June 27, 2012, 03:13:52 am
Yes, it was 4AM here and I was awake... Not "evening" per se, I agree.

Anyway, second link still not working here. Strange.
14  Using Arduino / Programming Questions / Re: Using a Timer interrupt with the Servo library on: June 27, 2012, 02:25:45 am
Dunno what's wrong, then. Been trying since yesterday evening :)
15  Using Arduino / Programming Questions / Re: Using a Timer interrupt with the Servo library on: June 27, 2012, 02:21:15 am
Thank you. The link to your site doesn't work, though...
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