What is this called?
#1
Posted 04 September 2011 - 02:49 PM
BUT… alas no. It has 6 connectors to it instead of the 4 I’m used to. Does anyone have an idea what this thing is called so I can Google it?
Also, do you know if it’s possible to get this etched strip in a roll… say 100 feet?
Thanks All
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#2
Posted 04 September 2011 - 03:08 PM
I believe it is called 'raster' or 'encoder strip', you can get it for cheap at eBay. Regarding the number of pins on the connector, it would help to see the back side of the sensor module - it may be just extra not-connected pins, or for example the encoder sensor may have two sensing elements to determine the direction of the movement, or to increase precision etc.BUT… alas no. It has 6 connectors to it instead of the 4 I’m used to. Does anyone have an idea what this thing is called so I can Google it?
#3
Posted 04 September 2011 - 03:57 PM
I believe it is called 'raster' or 'encoder strip', you can get it for cheap at eBay. Regarding the number of pins on the connector, it would help to see the back side of the sensor module - it may be just extra not-connected pins, or for example the encoder sensor may have two sensing elements to determine the direction of the movement, or to increase precision etc.
Thanks CW2. That was the phrase I needed. 'encoder strip' Unfortunately, the strip material is rather expensive. I just imagined it being made on huge rolls for the InkJet industry... not being $89 for 10 feet. But here is the backside of the circuit board in case someone else wants to mess with it. I also found this article that might be of help.
Messing with an Encoder
But it spawned another idea, I'll put into another topic.
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#4
Posted 05 September 2011 - 09:17 AM
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#5
Posted 05 September 2011 - 12:32 PM
2011-09-05_2058.jpg 27.79KB 16 downloads
This would be my guess.(see labels on photo)
The GND plane is pretty obvious - large filled area.
There is a cap between GND and what I would assume is VCC
VCC is also supplied to one pin of the sensor via a resistor. This would be a current limiting resistor for the LED side of the light gate.
The detctor side appears to have a connection to VCC and GND and two ouptuts. These are normally called A and B and are 90° out of phase. This allows you to work out which direction the sensor is moving.
If you think of the output as a 2-bit binaty value then the signal would 0-1-3-2 going in one direction and 2-3-1-0 in the other direction.
Mike P,
Thank you for the reply. Most of this fits in with what I’ve learned so far having started with the Sparkfun’s tutorial. It brings up a couple of questions if you or someone could help. I think the first thing that gets me second-guessing what I’m seeing is the additional stuff. In this case…
- there are two connectors with a total of 9 pins and I know no manufacturing engineer is going to let a high volume piece go out with things that aren’t needed.
- No capacitor was needed in the Sparkfun tutorial. All I know (so far) is… capacitors can store electricity and they act as some kind of filter for AC. What does it do in this circuit (just the technique name… I can look it up)?
- Taking a WAG… is this what’s called a “bandwidth filter”? And if so… what or why would we want to filter anything out of the signal?
BTW – What are you doing to insert the thumbnail?
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#6
Posted 05 September 2011 - 04:07 PM
In the tutorial you linked in your second post, there is a picture of almost the same sensor board (in the middle of the page, just above the sensor schematic) and the second (small) connector is described as "connector to paper sensor". A few lines below there is a photo of the back side of the board with colored traces, which are very similar to your board (I think only sensor outputs A and B are wired a little bit differently). The capacitor between ground and power supply is usually called decoupling capacitor.
- there are two connectors with a total of 9 pins and I know no manufacturing engineer is going to let a high volume piece go out with things that aren’t needed.
- No capacitor was needed in the Sparkfun tutorial. All I know (so far) is… capacitors can store electricity and they act as some kind of filter for AC.
#7
Posted 07 September 2011 - 01:42 AM
The decoupling cap serves to smooth out the power supply. It acts like a shock absorber on the supply voltage. Without it small spikes on the power supply would be created whenever loads were switched on and off and these spikes might be transfered to the output signal.
The spikes on the output could be mistaken for real output transitions and cause the encoder to lose its count.
I posted some code on the Wiki last night for a rotary encoder. Chances are that it would work fine with your strip as well.
http://wiki.netduino...oder-Input.ashx
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