Author Topic: Doubts about voltage margin (-/+5V) or (+/-10V).  (Read 4197 times)

Disidente

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Doubts about voltage margin (-/+5V) or (+/-10V).
« on: June 30, 2014, 07:26:29 PM »
Hi macpod. Just yesterday I order a Laserhark board to Barcelona (Spain). I hope to receive the order soon.

I have been reviewing the documentation regarding the LaserShark board, and I have some doubts. In the brief description you make of it, you say ...

"Lasershark v2.0 Specifications. ILDA-standard differential + /-10V 12-bit X and Y Adjustable output to get as close as possible to the spec."

and this picture say... (http://macpod.net/electronics/lasershark/images/lasershark_pinout_v2.jpg) descriptive that you contribute here. It appears that the voltage range is +5 / v-5v. Does that mean that the degrees of movement in the galvos are "limited" from suposed (-/+15V) to 1/3 of movement?

I hope recived my order soon.
Thank!
« Last Edit: June 30, 2014, 07:28:29 PM by Disidente »

Macpod

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Re: Doubts about voltage margin (-/+5V) or (+/-10V).
« Reply #1 on: June 30, 2014, 09:04:00 PM »
Hi macpod. Just yesterday I order a Laserhark board to Barcelona (Spain). I hope to receive the order soon. 




I have been reviewing the documentation regarding the LaserShark board, and I have some doubts. In the brief description you make of it, you say ... 




"Lasershark v2.0 Specifications. ILDA-standard differential + /-10V 12-bit X and Y Adjustable output to get as close as possible to the spec." 




and this picture say... (http://macpod.net/electronics/lasershark/images/lasershark_pinout_v2.jpg) descriptive that you contribute here. It appears that the voltage range is +5 / v-5v. Does that mean that the degrees of movement in the galvos are "limited" from suposed (-/+15V) to 1/3 of movement? 




I hope recived my order soon.
Thank!



The LaserShark for the X and Y channel DO follow the ILDA spec. the output range IS NOT "limited".

The +5/-5v indications in the picture are the potential of that pin compared to GND on the LaserShark board.

According to the ILDA spec, the X/Y signals are bipolar differential meaning you must compare the +X pin with the -X pin and the +Y pin with the -Y pin, not GND.

As an example:
1. If the -X pin is -5v and the +X pin is 5v, this is a 10v differential.
2. If the -X pin is 0V and the +X pin is 0V, this is a 0V differential.
3. If the -X pin is 5V and the +X pin is -5v, this is a -10v differential.


Please see:
http://www.laserist.org/StandardsDocs/ISP05-finaldraft.pdf

The specification confuses many because the "Voltage range" column for the  "X Axis (+)", "Y Axis (+)", "X Axis (-)", and "Y Axis (-)" states "+/-10V diff"

If you scroll down further in the specification you will see this is clarified with the following:
Quote
All signal receivers must have a true differential input stage! Unless otherwise indicated, the signal must always to be derived from the difference between the normal signal line and the corresponding inverted signal line. For example:

A differential voltage of +10V occurs if the normal signal line (+) has a voltage level of +10V with respect to the voltage level of the inverted signal line. (-)