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Openservo boards on 12 volts?

 
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subculture



Joined: 13 Aug 2006
Posts: 15

PostPosted: Fri Jul 13, 2007 12:41 pm    Post subject: Openservo boards on 12 volts? Reply with quote

Hi,

Can anyone please tell me if the openservo boards will work with 12 volts?

I'd be interested in using the board with some small geared motors I have. These are not high current, but they will not run well on 7 volts or so.

Thanks,

Andy
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robotjay
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Joined: 01 Aug 2006
Posts: 225
Location: Nebraska, USA

PostPosted: Fri Jul 13, 2007 1:40 pm    Post subject: Reply with quote

Andy,

The main OpenServo designs (v2.1 and the newer vX2) are 16V tolerant. The biggest issue you will face, though, are current limits and the resulting heat dissipation. My personal rule is that these boards can run at around 2A continuous, and up to 3A in short bursts.

I know it has been discussed time and time again, but I don't know if any sort of current limitimg has been implemented in the OpenServo firmware. The hardware is fully capable of doing this, it will just take a good coder to add this function to the source code.

I personally suck at coding, but maybe you (or others lurking these forums) are good at C programming, and can really help out with the firmware development for the OpenServo. Anyone out there? Talk to you soon.

-Jay
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eric_lmi



Joined: 08 Mar 2007
Posts: 41

PostPosted: Fri Jul 13, 2007 2:14 pm    Post subject: re Reply with quote

I tried 12v on openservo V2.1. there is no problem for a short time runing at 12v. but as Jay mentioned you need think about heat dissipation if your servo is always working in full power.

software firmware:
modify PID gains PWM output frequency, may allow you running openservo at higher voltage
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subculture



Joined: 13 Aug 2006
Posts: 15

PostPosted: Fri Jul 13, 2007 3:33 pm    Post subject: Reply with quote

Well the motors I want to run are under 4 watts (made by Maxon, good quality), so I think I'll be well within the limits of the current handling.

Andy
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robotjay
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Joined: 01 Aug 2006
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Location: Nebraska, USA

PostPosted: Fri Jul 13, 2007 3:50 pm    Post subject: Reply with quote

Andy,

Hmmmm... sounds like you're looking to make a homebrew DX-117. Wink I was just looking over the Maxon motors myself yesterday for that very reason. I wish companies like Maxon would post their product pricing on their websites... I just can't be bothered to type an e-mail or make a phone call.

Let me know if you find pricing for one of their high torque motors. Talk to you soon.

-Jay
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eric_lmi



Joined: 08 Mar 2007
Posts: 41

PostPosted: Fri Jul 13, 2007 5:21 pm    Post subject: Reply with quote

most of DC motors (RC servo used) allow over 12v i think, some of them is 24v+

i am designing a robot servo gearbox + case set, similar to DX-117, but will achive about $50/each with 30kgcm at 9.6v. gear design already finished and also found a good manufacture made few sample for me for testing.

high performance Maxon is really expensive, over $300, low performance model maxon is made in china, what is the point to buy it?

another question, can avr168 openservo work with encoder? a 8bit MCU is hard to release a $300 Maxon performance!!


a good diy combination is hitec 5995 gear/case +openservo + some japan coreless DC motor (sorry forgot the motor brand, will check it out when back home)
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subculture



Joined: 13 Aug 2006
Posts: 15

PostPosted: Fri Jul 13, 2007 7:13 pm    Post subject: Reply with quote

Well I pick the motors up surplus at shows, ebay etc. for just a few pounds each.

They're quite cheap that way. I find the quality of these motors is very high, the gearboxes alone are worth the price.

The reason I use these motors instead of a servo, is the application- model submarine piston ballast tanks.

The open servo board is ideal for proportional control of the tank (which is essentially like a large syringe). The tank plunger/piston is actuated using a threaded spindle, so I need a geared motor that can turn the spindle round and round, with an external pot for feedback (usually use a multi turn pot for this). Microswitches at each end of the tank ensure the piston tank doesn't stall against itself.

There are controller boards already available for this task, based on a magnetic encoder, but they cost about fifty quid each. The open servo board looks like an economic alternative for smaller piston tank designs.

Andy
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pgrosch



Joined: 11 Nov 2009
Posts: 1

PostPosted: Wed Nov 11, 2009 6:52 pm    Post subject: Re: Openservo boards on 12 volts? Reply with quote

subculture wrote:
Hi,

Can anyone please tell me if the openservo boards will work with 12 volts?

I'd be interested in using the board with some small geared motors I have. These are not high current, but they will not run well on 7 volts or so.

Thanks,

Andy


Any body tried 12V on new version 3

I bought some linear servos (firgelli 12 volts) but the controller died. I am thinking in replacing the controller with an openservo, but I have not found the maximum ratings (max volt and amp specs ?).

Thanks in advance.
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robotjay
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Location: Nebraska, USA

PostPosted: Thu Nov 12, 2009 9:20 am    Post subject: Reply with quote

pgrosch,

As stated above, the OpenServo is rated for up to 16v. The thing you need to watch is the current rating. The OpenServo is rated for up to 3A bursts.

According to Firgelli's website, the L12 model (which I am assuming you're using) has a peak current drain of:
Quote:
Stall Current: 450 mA at 5 V & 6 V, 200 mA at 12 V

The OpenServo will fit this application perfectly. You should order a few OpenServos and an OSIF through RobotFuzz and post the videos once you're done. I'd be glad to offer you any help you need along the way. Talk to you soon.

-Jay
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