Interfacing a Basic ASI Gauge

[Boeing 747 Flyer]

HI David,

You mention "using gearing"...

What does this mean exactly?

I understand how to use the IO Cards Servo testing software, this is no problem. It's more the mechanical side of things.

Also, the Hitec HS55 doesn't look lie it'll fit within my instrument. Is it possible to house the Servo BEHIND the instrument, and feed the needle movement with a small metal "Pole" attatched to the sevo?

Thanks, very much,

Jack =)

[fordgt40]

Jack

If your ASI needle needs to move through 360deg and the max typical range of the servo is 180deg then you need to install gears such that for each deg of servo movment then the ASI needle moves 2 deg - ie a ratio of 2 to 1 or to put it another way you need twice the number of gear teeth on the servo shaft as is on the needle shaft. Follow this link for a practical example

http://www.737ng.co.uk/djb/brake_pressure_gauge.pdf

David

[Boeing 747 Flyer]

I understand. If the Servo only moves 180 degrees,then you'll need to "multiply" its working efforts, by adding gears.

I think I understand the eletronic connections now. It is like this:

PC -> USBServos -> Servo (Hitec HS-55) -> Instrument

Is that correct?

Also, the testing software. On the interface, you can move the servo by either using the "sliding control" at the bottom, or using the manual entry of a number between 0-1024. I have a question about this... If I entered, say "5" into this box, would it move the servo to "position 5", or through a RANGE of 5 (eg 0-5)?

Thanks alot,

Jack

P.S: That gearing photo helped. Are there any methods to work out the number/size needed?

[fordgt40]

Jack

PC -> USBServos -> Servo (Hitec HS-55) -> Instrument - yes
If I entered, say "5" into this box, would it move the servo to "position 5", or through a RANGE of 5 (eg 0-5)?
It will move to position 5 within the range of 0 to 1024

Are there any methods to work out the number/size needed - Only simple maths as outlined above, however, if the ratio is 2.5 to 1 then go for 3 to 1 on the gearing to give you extra needle travel as servos can be a bit jittery at their extremes of travel. Having decided on the ratio then find matching gears. If 3 to 1 then the gears should have 30/10 or 36/12 teeth respectively
David

[Boeing 747 Flyer]

Right that's awesome.

Also, there are many different variants of the Hitec HS-55. Which one should I buy? There is a "mini" version, larger version... Etc.

[fordgt40]

Jack

Whichever you think appropriate

David

[Boeing 747 Flyer]

Jack

Whichever you think appropriate

David

Right okay, I'm just worried incase there are any mechanical/electronic differences I should look out for. Anything that won't be compatible I should be aware of?

Thanks,

Jack

[fordgt40]

Jack

Only size and extent of rotation are relevant for this purpose. As advised, I use the Hitec HS-55 which as far as I am aware only comes in one sub micro size, not "mini and larger" as you suggested earlier

David

[Boeing 747 Flyer]

Hiya,

If you type in Hitec HS-55 on Ebay you'll get loads of different Models called "HS-55"

Also, some versions say things like "0.18 / 0.14 sec @ 60deg"... Shouldn't that be 180 degrees?

[fordgt40]

Jack

Sorry, but I would not use Ebay as an authority

I buy my servos from a local hobbyshop - safer!
No idea about "0.18 / 0.14 sec @ 60deg"... , means nothing to me

David