Centroid Community CNC Support Forum

Acorn Spindle Encoder Basics


1. Encoder Type:
Centroid Acorn CNC controller Encoder input requires quadrature, differential encoders for Spindle encoder use which operate on 5VDC. This is the most common type of encoder. Encoders labeled "TTL type" (single ended, non differential) are unsuitable, and fortunately are rare and converter boxes are not recommended.

2. Encoder Signals:
a) The following signals must be present and wired: A, /A, B, /B, Z, /Z, +5VDC and ground.

Note: The Z channel is sometimes labeled as I, C or "marker". The "/" symbol may also be
expressed as "-", "NOT" or "!" or a line over the letter, it means the signal is the complement
(opposite) of the channel specified.

b) Signal levels:
The "low" signal level must be less than 0.5 VDC and the "high" signal level must be at least 3.5 VDC. ACORN supplies around 50mA that is typical of most encoders.

3. Spindle Encoder Resolution:
Typical Machine tool applications (milling machines, lathes and routers) require at least 500 line (2000 counts per rev) encoders, We recommend any where from 500 to 2000 line (= 2000 to 8000 counts per rev) encoders for spindle applications. To achieve reasonable accuracy for good threading and rigid tapping.

4. Also consider the max. frequency for spindle encoders, this relates to the useable Maximum RPM that the encoder can operate at.
Most cheap encoders are limited to 3000rpm with 2000 lines, with 1000 lines to 6000rpm.
Rigid Tapping works great even at low line counts such as 400 or 500 line (1600 counts per rev, 2000 counts per rev)

Encoder wiring at the Acorn
DB9 Body = Cable Shield

Pin Function
1 No Connection
2 GND
3 Z\
4 A\
5 B\
6 Z
7 A
8 B
9 +5 VDC
related Acorn Spindle Encoder thread.
viewtopic.php?f=60&t=1925

We sell 2000 line (8000 counts per revs) encoders that accept common sized motor encoder shafts on our website.

2000 Line Encoder (8000ppr)
This differential encoder not only suppresses noise in the system that can be harmful to encoder signals, but also outputs a quadrature signal giving 8000 counts per revolution of the motor. This is ideal servo motor applications for machines already equipped with DC brush servos to enhance the speed and precision of the machine. Available in 6 mm, 1/4", 3/8", and 1/2" hollow shaft sizes These are really geared for servo motor use. While these can be used for spindle applications consider buying an enclosed (dust / water proof) Koyo encoder for a Spindle application.
https://www.automationdirect.com/adc/se ... ential)%22

Question: Somehow the encoder pigtail was damaged. What are the wire colors of the encoder pigtail?

Answer:
Pin Signal Color
1 A Blue
2 A/ Blue/Black stripes
3 B Green
4 B/ Green/Black Stripes
5 Z Violet
6 Z/ Violet/Black Stripes
7 Vcc Red
8 GND Black
9 Shield Heavier Black wire

Encoders labeled "TTL type" (non differential) will not work with our control. We have 2000 line (8000ppr) encoders in 6 mm, 1/4?, 3/8?, and 1/2? hollow shaft sizes available if you need to swap yours out.

You would need a differential quadrature output the same as the encoders (minus the Z channel). Do you have a manufacture and model number for the scales you wish to use? Please note that each axis will still need an encoder signal.

10 mm encoders are in stock. we also have 10,000 line encoders in stock as well. call or email for shaft sizes available.
also proper shielded encoder cable and shielded vfd with drain is in stock at very affordable prices.
also new Oak and ALlin1dc schematics sets are available along with the latest Oak and Allin1dc installation and operator manuals on this page
http://www.centroidcnc.com/operator_manual.html

new video on encoder mounting by martyscncgarage.

https://youtu.be/bd2GzrBAn9A?list=PLXhs ... STDELrnNx2

I could find on this series of encoder actually publishes the low and high signal level specs! So, what's the real deal with all this signal level stuff?!

Thanks in advance for any assistance you can provide!
[/quote]

3.5 to 5 volts is what you want.. you get any lower than that and you'll get differential errors.
attached is dynapar endcoder spec sheet. centroid uses the 2000 line (8000 count per rev encoders) as a minimum spec encoder.
I've been personally using a Quantum Devices 10,000 line (40,000 count per rev) encoders on all installations with Allin1DC for the last few years with great results.
attached is a pdf photo. you can buy these from centroid or other sources as well and that is what i recommend to use.

Does the recommendation for at least 1000 line encoders apply to mill & lathe spindles as well as axis servos?

edited to add: Sorry guys, looks like I need to RTFM more thoroughly before asking questions! I just saw that the recommended encoder for the Acorn is 2000 lines.

Milton,
I would not go less than 1000, 2000 is better spindle or servo motors
automationdirect.com is a good source for encoders as is Centroid. Try and stay away from ebay, its not worth the trouble....
Marty