[simpits-tech] MarvMan and Craigo Fixed Stick Update
Marv De Beque
simpits-tech@simpits.org
Sat, 21 Dec 2002 08:45:38 -0500
Hmm, clever idea. I may roll my own circuit first, but I'll let you know.
Marv
On 12/20/02 9:34 PM, "Craig Rochester" <johncraigroch@msn.com> wrote:
> Very nice!
>
> You could use the output from a PC's sound card --> stereo amp for the kHz
> VAC excitation. I've got a little exe that sends a sine wave and you can
> adjust the frequency and amplitude.
>
> Craig R.
>
> -----Original Message-----
> From: simpits-tech-admin@simpits.org
[mailto:simpits-tech-admin@simpits.org]
> On Behalf Of Marv De Beque
> Sent: Friday, December 20, 2002 8:02 PM
> To: simpits-tech@simpits.org
> Subject: Re: [simpits-tech] MarvMan and Craigo Fixed Stick Update
>
> Yeah, just did a quick test of one of the coils now and it looks like it
> works. I need to build the circuit so I can properly test it with installed
> in the transducer base.
>
> All I had was a square wave generator to excite it, so the output was a set
> of spikes. Still, as I moved the core inside and out it changed amplitude.
>
> Next weekend I should have it wired up! Well, might get both axis wired up,
> too. ;-)
>
> Marv
>
> On 12/20/02 7:07 PM, "Craig Rochester" <johncraigroch@msn.com> wrote:
>
>> Marv,
>>
>> Holy *&^%! Winding your own LVDTs!!! Now that's impressive!
>>
>> The variable displacement for pitch-up and pitch-down sounds great!
>>
>> Thanks for the update.
>>
>> Craig R.
>>
>>
>>
>> -----Original Message-----
>> From: simpits-tech-admin@simpits.org
> [mailto:simpits-tech-admin@simpits.org]
>> On Behalf Of Marv De Beque
>> Sent: Friday, December 20, 2002 5:45 PM
>> To: simpits-tech@simpits.org
>> Subject: Re: [simpits-tech] MarvMan and Craigo Fixed Stick Update
>>
>> Well I have not been very impressed with the results of the load cells and
>> the one version of strain gauge that I have. I have ruled out the load
> cell
>> as it does not have acceptable accuracy and repeatability in the null
>> position (hands off the grip should return to center position).
>>
>> I have ordered a different strain gauge set to test which should be in by
>> mid January. This set is a little more work to install, but supposed to
> be
>> much more accurate than past experiments I have tried.
>>
>> Over the next week I am going to test some LVDT sensors. Actually, I am
>> going to roll my own for this test. I spent a little time this morning
> with
>> our companies bobbin winder in the lab. Last night I cut two bobbins out
> of
>> nylon and spun them with about two hundred windings of 36 gauge
> transformer
>> wire on each coil (there are three coils per sensor).
>>
>> I have ordered some special interface or signal conditioning ICs that
> should
>> arrive some time after Christmas. I'll bread board a circuit and run the
>> same series of tests on the LVDT system as the other load cells. By then
> I
>> should have the other strain gauge parts in to test that system.
>>
>> So far I can say that the strain gauge system holds promise in that I
> think
>> I can get it to work satisfactorily, but it will be more labor intensive
> to
>> build than LVDT. However, LVDT sensors are expensive. My single piece
>> price on those is $92 each! Now you see why I am rolling my own for
> testing
>> purposes. The interface circuit is also a little more complex.
>>
>> I completed a mechanical design enhancement that better replicates the
> feel
>> and movement of the grip relative to the transducer base. As you may
> know,
>> the real side stick has different amounts of physical movement of the grip
>> depending on direction it is moved. Pushing forward has virtually no
>> movement at all, but pull back and it can move 1/4"!
>>
>> I have been able to replicate that movement precisely. What's more is it
> is
>> adjustable! However, you need to take the base apart to get at the set
>> screws that control the amount of flex. I plan to set it to factory specs
>> when it leaves my place if I use the design. Unfortunately, it requires
>> more parts and machining to do it, but we will see.
>>
>> I must say that this project has taken a lot more engineering time than I
>> had first budgeted. The good news is that I have been slowly refining the
>> design so it will be "right" when it is done and offer significant amount
> of
>> realism.
>>
>> The downside is probably going to manifest itself as price creep. The
> worst
>> case scenario is the LVDT sensor system. That could cost an additional
> $150
>> to $200 depending on actual costs of components. Obviously, that is my
> last
>> choice for a system if I can't get satisfactory results from the strain
>> gauges.
>>
>> Marv
>>
>>
>>
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>
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