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1  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 27, 2011, 08:17:16 pm
Thanks guys for the replies. Pulled the pin and it kept going. Unfortunately don't have time to interface with a pot or order a new one.

The load varies greatly because it is used to lift objects of different weight.

It looks like they only draw 200-450mA max so a large transistor or small relay would do.

If you're dead luck the servo will do nothing on power up and therefore stay where you left it.

______
Rob


Can you explain how I can hook up a transistor like an electronic switch to control the power?
2  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 10:55:15 pm
Another logical option would be to return to the center position.
If by center position, in my case, you mean between fully extended and retracted then that's what I currently have it setup to do. But I really need it to stop at the current mechanical position.

Also, I read up that some digital servos remember the last set position and continue to move to that position even if the pulse is cutoff. That appears to be my situation. Looks like I will have to cut the power off and assume everything will act normal when re-powering. Any ideas on how to set that up?
3  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 10:37:27 pm
Never mind, read up on it here:

http://www.servocity.com/html/how_do_servos_work_.html

But I am still assuming that once the pulse stops, it is stuck at the last position?
4  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 10:28:45 pm
Yea, going out of the way just to cut off the power does seem a little drastic especially for such a simple request. Well see...

Just to be clear:
signal pulse = movement
detach = no signal pulse
therefore no movement

Standard for servos correct? How do the pulses actually control the different positions?
5  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 10:09:04 pm
R/C servos were never designed to operate with no signal input pulses yet with power still applied. Their behavior in that condition is not defined, and may even very between manufacures and models of servos.


Lefty


Yea, not sure why it keeps moving even without a signal input pulse. Any other suggestions? Should I just set up something to cut off the power?
6  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 10:03:23 pm
It may just shut the class down but not stop the timer generating the pulses.

I'm thinking that may be the case. I never tried pulling the wire out because I assumed using detach would do that for me. I'll try tomorrow in lab.

The actuators are pretty sweet. Thing is, this is for a senior design project, funded by the university. I get to keep whatever we don't use... accidentally ordered an extra pair  smiley-cool
7  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 09:56:36 pm
Assuming you are using the servo only version I would set up a function that works similar to fading an LED.  Adjust the fade rate to the servo speed.  That way the servo is never very far from the set point.  Depending on load, precision and speed this may need some tweaking. 

Can you further elaborate? I think I get what you're saying but I may be wrong. Are you suggesting I move the servo in "steps" in which I can keep track of the position? The problem is that it cannot be time dependent, like as you mentioned, unfortunately  in my case the load will vary almost every time.
8  Using Arduino / General Electronics / Re: How to stop servos before reaching position on: April 25, 2011, 08:30:29 pm
You might try using the servo detach function.

http://arduino.cc/en/Reference/ServoDetach

Thanks. I thought the same, but unfortunately it didn't work. I'm assuming once the servo is sent the "pulse" to move to a specified angle, even after you detach it, it is still set to move to that position, and since still powered, won't stop until it gets there (probably bc of the control circuitry on the actual servo). Any other thoughts?
9  Using Arduino / General Electronics / How to stop servos before reaching position on: April 25, 2011, 07:04:14 pm
I need help in stopping a servo. I'm using a linear servo found here (-R option):

http://firgelli.com/Uploads/L12_datasheet.pdf

Basically, it works like a traditional servo. Black, red, white connections. Pulse sent to control "degree" 0-180 of the servo, in this case retracted and extended. I'm using the servo library included with the arduino software.

Since linear servos take a reasonably longer time to reach the specified position, I was wondering if I could somehow interrupt and stop the servo before it reaches the positions. For instance, if the servo is fully retracted and the user specifies the servo to fully extend, along the way I want the user to be able to stop the servo at any position during that time.

Do I have to set up some sort of enable pin that controls the power directly to the servos?
10  Using Arduino / General Electronics / Re: Charging battery pack through DC jack on: April 25, 2011, 04:54:16 pm
I'm using an arduino enclosure with the circuity and battery connected in the enclosure. I want to be able to charge the battery by plugging the charger through the DC jack on the board rather than installing another DC jack.
11  Using Arduino / General Electronics / Re: Charging battery pack through DC jack on: April 25, 2011, 04:14:47 pm
Quote
Is there a way to bypass powering the Arduino and just access the power through Vin

Only by hacking the arduino board with a scalpel and soldering iron. See the arduino schematic to find out where to cut tracks.

If I just disconnect the power pin from the board and then connect that directly to the battery do you think that will work?
12  Using Arduino / General Electronics / Charging battery pack through DC jack on: April 24, 2011, 06:16:45 pm
Right now my Arduino Uno is being powered by a 7.4V Lithium Ion battery pack. The battery pack is connected to a switch. When the switch is turned on, the Arduino is powered through Vin.

I want to be able to charge the battery pack through the DC barrel jack of the Arduino. From my understanding, when powered through the DC jack, the Arduino is powered with regulated 5Vs, and the unregulated voltage can be accessed from Vin.

The problem is that I am using a smart charger for the Lithium Ion Battery and want to be able to safely charge and utilize the charging indicator on the smart charger. But when plugged in, it also powers the Arduino board. Is there a way to bypass powering the Arduino and just access the power through Vin.

Also, can someone further explain the 3 connectors of the DC jack. I saw a post explaining it but can someone give me an example. Thanks.
13  Using Arduino / Project Guidance / Charging Li-Ion battery without removing on: April 15, 2011, 12:44:30 pm
The battery needs to be able to be easily charged without the user having to remove the battery from the device.

I included some diagrams that I made quick in paint. I'm trying to have the Li-Ion battery power both the micro-controller and servos. I was thinking that when the switch was OFF (not connected), the charger can be plugged into the circuit (DC connectors) without removing the battery.

I'm using a 7.4V Lithium Ion battery and a Li-Ion smart charger:
http://www.all-battery.com/universalsmartchargerforli-ionpolymerbatterypack37v-148v1-4cells.aspx

Would the charger harm the micro-controller if the switch was ON? What do you think, will this work?
14  Using Arduino / General Electronics / Help powering Adrduino UNO and servos from Lithium Ion battery on: April 15, 2011, 09:48:41 am
I need some help for my senior design project. The general idea of the design is I am using the Arduino UNO combined with the VRbot voice recognition module to control two linear servos/actuators.

Firgelli L12 -R Linear Servos:
http://store.firgelli.com/l12-r-linear-ser12.html

I used an H-bridge IC L293D and followed the tutorial here to forward and reverse the actuators:
http://luckylarry.co.uk/arduino-projects/control-a-dc-motor-with-arduino-and-l293d-chip/

I have everything working correctly but I need some help on making it portable. I'm using a 7.4V 2200mAh rechargeable lithium ion battery to power everything found below:

Li-Ion 18650 7.4V 2200 mAh Rechargeable Battery module with PCB:
http://www.all-battery.com/li-ion1865074v2200mahrechargeablebatterymodulewithpcb.aspx

How can I safely and correctly power both the servos and Arduino board using just one battery. Can I connect the battery directly to both the servos and Vin of the Arduino? Any help would be great!
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