Digital Tach

[coldspot]

"Hobbico"

"Digital Mini-Tach"  #HCAP0400

Hello, I have this mini tach from RC Combat flying Days gone by.

I'd like to mount this up on the tower pointed at prop/blade from behind/under.

I wonder if anybody knows how far I could move the little sensor, (how much wire I could add between it and diplay-readout)?

Unit runs on 6 VDC.

I'll run a power line up ,so I could add these wires also, but I'll need to, to add other idea's anyway. (Moveable video camera mounted under weathercover behind Ametek).

I'd like to be able to watch the RPM's while also seeing Amp's/Volts.

Right now only able to watch mill thru Security Video camera aimed at it,  it's about the same as watching the street. JUST LIKE TV, a waist!!!

So if anybody has any thoughts or idea's....

please share

Thank you

[coldspot]

Admin-

Why can't we add pic's to first new post/storie?

Anyway heses some pic's of Tach













Just wondering how far I could lengthen sensor wires?

[TomW]

Duh;

Admin-

Why can't we add pic's to first new post/storie?

You are just not looking in the right spot for the "insert photo" text.

I know its more fun to complain than spend a minute looking for the button to insert pictures.

T

[ghurd]

The tech guys at a bike speedo manufacturer told me the wire can be "about as long as you want".  The RPM on bikes is a lot less.

They also said a stronger magnet could placed farther away from the sensor. Maybe 1 magnet on the back of 1 blade?

Not sure if that helps, or if they both operate on the same principles.

G-

[wdyasq]

All of the small R/C air-o-plane tachs I am familiar with are optical.  The ones I have used have a 2/3 blade switch.

Ron

[coldspot]

"All of the small R/C air-o-plane tachs I am familiar with are optical.  The ones I have used have a 2/3 blade switch."

Ron-

Yes, thats what I got.

can I lenghten the wires?

Admin- I looked for more than a min.

[johnlm]

I have one of those tachs also from my RC flying days.  The sensor on those is optical. However those tachs are not very good for prop speeds as slow as windmills turn.  The resolution is in 100 RPM increments so you would only get close approximations.  I have tried getting in the shadow from the sunlight of the turning prop blades with my tach like that with so-so results.  If you mount the sensor up on your tower it might work alot better if your blades are dark in color (black, dark blue or brown).  Anything lighter in color might not provide enough contrast against a blue sky for the sensor to pick up.  I think I would try for the cheapie electronic bike speedometer that several have used that is a magnetic pickup.  One caviat to the bike spedometers is they start misreading when the RPMs get up around 600  with long lead wires attached.  Ive looked at the waveform on the sensor line (reed switch which pulls a logic high to ground) with an oscilloscope and it appears the logic high pull up circuit cannot recover to a high state fast enough to handle rep rates above 10 HZ (600 RPM).  Probably high capacitive (inductive?) loading due to the long lead wires is too much for the low current drive circuit to pull it up faster.

You may have the same if not worse problems with long leads on the optical tach.

Johnlm

[wooferhound]

Why can't you monitor the AC frequency coming from your generator, and calculate it from that ?

[Chiron]

That would take all the sport out of it Woof

[coldspot]

No AC coming out. (PM Ametek MiniMill).

Just was hopefull I had something/else to add/use.

[wdyasq]

I think you could run the wires as far as you dared.  If you put a 200 division optical disk - black/white/black/white - for the sensor to read, you would be adding a 100 multiplier to the input and could get fairly accurate readings I would think.

Ron

[Opera House]

Another method you might consider is pointing a LED at the optical sensor and having a circuit that sends electrical pulses to the LED.  A gear could be placed on the shaft with a magnetic pickup and then amplified be an op-amp.  Then you won'd be destroying anything.  If this was an alternator, the ac out could just be fed to the LED with a diode and resistor.

[hvirtane]

You are just not looking

in the right spot for the

"insert photo" text.

The button to insert pictures for

the new post is on the right hand

of the page. Under 'menu' and your

'user info' etc. It is confusing that

it is different when you are adding

a comment.

- Hannu

[coldspot]

Hannu-

Thank You

"The button to insert pictures for

the new post is on the right hand

of the page. Under 'menu' and your

'user info' etc. It is confusing that

it is different when you are adding

a comment."

Learned something new today!!! lol

And it'ss only a half hour into the  new day!!! LOL