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1  Using Arduino / Motors, Mechanics, and Power / Re: Servos not reacting to PWM (independently powered) on: December 26, 2013, 11:02:40 am
Note that a servo needs a PPM signal which is what the examples in the Arduino IDE generates.

Your issue is likely a grounding problem as stated above, make sure that the negative side of the walwart is connected to the arduino's ground pin.
2  Using Arduino / Installation & Troubleshooting / Re: Arduino Mega Pro (Sprakfun) on: October 03, 2013, 10:29:45 pm
Old post but any ideas?
3  Using Arduino / Project Guidance / Re: Bluetooth? Robotics controller on: July 07, 2013, 09:24:11 am
Also, look into Xbee Modules for wireless communication and Processing to actually send the commands.

Processing------>USB Port--------->Xbee USB Adapter------->Xbee---------------"radio waves"---------->Xbee----->Arduino onboard Robot
4  Using Arduino / Motors, Mechanics, and Power / Re: 12 volt relay at 24 volts at 20 amps on: July 07, 2013, 01:29:47 am
It should work as long as you switch light loads, however if you need your setup to be absolutely  reliable for whatever reason (safety, etc) then get a relay rated for 24 V.
5  Using Arduino / Motors, Mechanics, and Power / Re: 12 volt relay at 24 volts at 20 amps on: July 06, 2013, 01:07:58 pm
For what its worth I am using a similar (probably the same) relay from Radio Shack on a RC Lawnmower. Power source is two 24V batteries, however the contacts are closed with a 12V lined center tapped from the battery bank since I noticed the relay getting hot when switched closed with 24V powering the coil (could also add a small resistor in series).

The motors are controlled with a Sabertooth 2x25 and are pulling around 15 amps each at full throttle......that is 30-40 amps at 24 V through the relay, I have not experienced any issues yet

Keep in mind that in my setup the contacts are only closed at power on and opened at power off and are not used for switching  motors on and off.
6  Using Arduino / Project Guidance / Re: Whats the difference in models? Im a Noob on: July 03, 2013, 08:42:03 pm
I'd pay the extra and use a MEGA that way you have plenty of I/O pins to play with

What are you building btw?
7  Using Arduino / Project Guidance / Re: Turning heavy load on: July 03, 2013, 08:39:00 pm
We need pictures of your setup to make any suggestions......
8  Topics / Robotics / Re: How does wheel size affect speed??? on: June 30, 2013, 10:41:08 pm
A larger tire will require more torque output from the motor, this will cause the motor to slow down for a given voltage which in turn increases power consumption by said motor.

How much the motor slows down will determine wether the bot will move faster or slower for a given wheel size.


In other words you can oversize a tire when trying to get more speed out of a bot and actually slow down the bot

Speed = diametertire*pi*angular_velocitytire

If angular_velocity decreases more than the diameter increases then speed will decrease, the other way around speed increases
9  Using Arduino / Project Guidance / Re: Long Distance Wired Analogue Control Question on: June 29, 2013, 03:19:26 pm
Built a ROV as a senior project last year (Mech Eng. project). Ditch the analog input and send serial data down the line using RS485, this requires an Arduino on the surface to read the analog inputs and send this data down the line to a Arduino onboard the ROV. Look into the MAX485 chips and the LTC490 IC's, both are good search terms in google ( I went with the LTC490, ~$4/IC).

10  Using Arduino / Project Guidance / Diode in SERIES with Relay Coil on: June 22, 2013, 10:00:21 am
What would be a good diode to prevent a NO relay from closing when reverse polarity is applied to a circuit via a drunk wiring said circuit by placing a diode in series with the coil, assuming relay current is less than 300mA?

Note: This is NOT for back EMF protection, just trying to prevent frying a SABERTOOTH if  wired up backwards and flip on the switch which controls a relay
11  Using Arduino / Project Guidance / Re: Using 24V and 12V from batteries in series on: June 10, 2013, 10:47:18 pm
A quick google search on subject made me hesitant. I am just checking to see if anyone has experience with this.

Since the load on my 12 V line is much less than the load on the 24 V line I feel that I think that I should be fine, however I am not certain as one battery will technically discharge faster than the other. This may not even be an issue?

Has anyone done something similar?
12  Using Arduino / Project Guidance / Using 24V and 12V from batteries in series on: June 10, 2013, 10:04:27 pm
I am in need of 24V and 12V for a RC Lawnmower project. What are the possible issues/concerns with using both 24V and 12V from same two batteries?

The 24V load will be in excess of 40 Amps but the 12V load will be less than 2 Amps. The batteries are 12V Deep Cycle batteries (75 Ah).
13  Using Arduino / Project Guidance / Re: Destroyed Pololu 36v20 CS on: June 10, 2013, 09:03:38 am
Final bump
14  Using Arduino / Project Guidance / Re: Destroyed Pololu 36v20 CS on: June 09, 2013, 07:10:45 pm
Also, when I cut the wires from the motor drivers to the Arduino (PWM and digital for direction) the onboard LED glowed as they should. I then put an amp meter between the output of the Arduino to the input of the motor driver as was pulling 90mA which is obviously what damaged the Arduino.

The motor driver PWMH and DIR pins seem to be shorted to ground (not from my wiring however)
15  Using Arduino / Project Guidance / Re: Destroyed Pololu 36v20 CS on: June 09, 2013, 07:06:16 pm
I've doubled and tripled check the rest of the wiring and have removed the capacitor with no luck. I also continuity tested power and ground before hooking up power to ensure no shorts....................I can't seem to figure out what went wrong if its not the pins I hooked the caps or the cap the I wired in reverse.

The power source is two 12V batteries in series and this did not do any visible damage to the 470uf cap wired in reverse, makes me wonder if a trace was blown in the transient process after power was hooked up?
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