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Date: Fri, 20 Jan 2006 05:55:23 -0700
From: Dale Rogers <dale.r@cox.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Attn Jim Maher: Re: [FlyRotary] Re: Max static with
 an IVO?
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Dave,

   It would be a rare ammeter, indeed, that would have a "highest
current" indicator.  Using an ammeter to indicate end-of-travel relies
on the fact that an electric motor draws the most current when almost
stalled.  Thus, a motor that is only pulling 3A to turn the blade
can be expected to jump up to 6 or more amps as the load increases
when the mechanism approaches its limits.  Depending on how quickly
the motor drives the mechanism, you could see the current rises over
a few seconds as it approaches end-of-travel.

HTH,
Dale R.


David Staten wrote:

> Jim...
>
>  I am following up on a previous post from November that is attached 
> below. You discussed using an ammeter and resistor to indicate 
> relative power draw as an indication of how many amps your IVO was 
> requiring.
>  
> One question. Is this indication (using the equipment you have 
> selected) ONLY when current is flowing? or does the needle stop where 
> it last was indicated (as in, to make an adjustment that only toggles 
> the switch for a moment, do you have to take time out at look at that 
> gauge that very instant, or does it have some "memory" of position, 
> like a trim indicator would?
>  
> Im guessing its a momentary indication, but wanted to ask anyways.
> Dave
>
>
> James Maher wrote:
>
>> Sure thing John.
>> The link below is for the one that I am using.
>>  
>> http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=276342&e_categoryid=643&e_pcodeid=03901 
>> <http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=276342&e_categoryid=643&e_pcodeid=03901>
>> There are several styles but I like this one because it shows 
>> direction and relative amount
>> without any actual values.
>> You will have to insert a 0.015 ohm 5 watt resistor in series with 
>> one of the wires that drives the motor, as a current sense. The meter 
>> is then connected across this resistor.
>> I used the one in the link below, also from Mouser.
>>  
>> http://www.mouser.com/index.cfm?&handler=data.listcategory&D=* 
>> <http://www.mouser.com/index.cfm?&handler=data.listcategory&D=*>71LVR50.015*&terms=71-LVR5-0.015&Ntt=*71LVR50.015*&Dk=1&Ns=SField&N=0&crc=true
>> This was not all my idea.
>> I saw a gentleman at Oshkosh a few years ago with an old ammeter that 
>> did the same thing.
>> I just updated to the newer style meter.
>> It beats waiting for the circuit breaker to pop.
>> Jim
>> *//*
>>