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Author Topic: [solved] is this possible with arduino uno?  (Read 1018 times)
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Hey guys, I got the arduino uno with the project kit that came with a lot of components and a project book so I can learn the scripting for all this. I have almost finished the book so I have learned a lot. But I am still very much a beginner. I bought this because of a specific project I'm working on which will end with 7 servos and many LEDs (maybe 15 LEDs and 2 premade LED boards that I got here http://dx.com/p/2w-9-smd-led-126-lumen-6500k-white-dome-light-dc-12v-51001 ). Here's my thought, I will only need 9 LED's to be controlled by the Arduino (on when a specific servo is one position and off when it is not). All the other LEDs can just stay on constantly; so can I just plug up power directly to the constant LEDs but have the same on/off switch for the arduino? I just don't want to have a bunch of on/off switches. As for the servos: there will only be 3 different actions.

Servo # 1: program 1
Servo # 2, 3, 4 ,5: program 2
Servo # 6, 7: program 3

Can I just put the same command wire connected to all the same servos with the same command to save outputs? For Example:

output pin 9 to Servo 1
output pin 10 to Servos 2, 3, 4, and 5
output pin 11 to servos 6 and 7

would that work?

Thanks for your help!
« Last Edit: January 18, 2013, 08:57:59 am by JacobGates » Logged

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Quote
output pin 9 to Servo 1
output pin 10 to Servos 2, 3, 4, and 5
output pin 11 to servos 6 and 7

would that work?

Probably. Note that servos usually can't be powered from the arduino.
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That LED requires constant current driver so if you power that driver and arduino with one supply and have a switch on that supply, you just need one switch. I imagine if servos 2 3 4 5 are doing the same thing then you can control them with one pin. Powering 7 servos directly with arduino is out of the question. You will tap into the one supply you use to power everything. The servo needs to accept 5V inputs.
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okay so because of the amount of servos I will need to have the servos attached to a separate power supply. So then I will have 2 power supplies: one for arduino and the other for the servos?
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okay so because of the amount of servos I will need to have the servos attached to a separate power supply. So then I will have 2 power supplies: one for arduino and the other for the servos?

Depending on the servo and the LEDs. The LEDs are rated at 12V so you can drive them up to 12V. I would recommend a constant current driver to match the LEDs.This driver probably needs up to 12V supplied to it at 167mA per LED light (I think I remember reading 12V 2W). This 12V power supply can also power the Arduino. Arduino has a 5V regulator so it will take the 12V and regulate it to 5V for the arduino. You can also use the 12V supply to power some 5V regulated supply to power all the servos. You need to sum up all these current requirements to see what current rating that 12V supply needs. Although Arduino has 5V regulated supply, it outputs no more than 500mA (I'm guestimating) so you can't power all servos with arduino 5V pin.
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Depending on the servo and the LEDs. The LEDs are rated at 12V so you can drive them up to 12V. I would recommend a constant current driver to match the LEDs.This driver probably needs up to 12V supplied to it at 167mA per LED light (I think I remember reading 12V 2W). This 12V power supply can also power the Arduino. Arduino has a 5V regulator so it will take the 12V and regulate it to 5V for the arduino. You can also use the 12V supply to power some 5V regulated supply to power all the servos. You need to sum up all these current requirements to see what current rating that 12V supply needs. Although Arduino has 5V regulated supply, it outputs no more than 500mA (I'm guestimating) so you can't power all servos with arduino 5V pin.

Okay just one more question. Thank you for all your help by the way. If I had a 12V supply and I connected it directly to the servos would I need something else to prevent to much power going to the servos? resistor maybe?
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You would need to read the sticker on the servo first. It tells you everything about how to power it. Post what you see on the sticker. You will likely need a 5V regulator if your servos run on 5V.
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You would need to read the sticker on the servo first. It tells you everything about how to power it. Post what you see on the sticker. You will likely need a 5V regulator if your servos run on 5V.

well the only servo I have at the moment is the only one that came with the arduino kit and it does say 5V:

1= GND
2= Signal
3= 5V

I'm just not completely sure how everything flows and just making sure I kill something because of ignorance. If I have a battery pack of (just for the sake of this conversation) 4 AA's... would that power all 7 servos and the arduino without anything to regulate power?
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There is a circuit inside the servo to control its orientation as commanded by Arduino. If the servo says 5V, I would give it 5V. Try 4 AA rechargeable batteries instead. They add up to about 4.8V so it's closer than 6V to 5V. Then you don't need a regulator.
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I don't think you connected the grounds, Dave.
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Servos are typically 6 volt-tolerant. They're designed for R/C models, where four AAs used to be the norm.
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sorry, i haven't replied in a day or two. My job had me work a lot of hours.

thank you guys. You have taught me a lot and I'm pretty confident in this build. Can't wait to get started.
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