So 1/2 hour after my previous post,

Lasers
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So 1/2 hour after my previous post, the Smoothieboard 5XC (although the M5 is faulty on this, so we may as well consider it a 4XC) has just arrived.

A big thanks to @Arthur_Wolf for designing & developing this board.

Now, onto the fun part. Figuring out what I have to do with it.

So along with my previous post (https://plus.google.com/+YuusufSallahuddinYSCreations/posts/3sMrHbN6WF5) I should be on the road to conversion shortly. As soon as I figure out what is necessary to buy/attach/do.

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Based on your previous post you need a middleman board as @Alex_Krause ​ said. That’s to convert the cables types. Then you will need a logic converter. Take a look at my collection on K40 upgrades.

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Thanks @Ariel_Yahni_UniKpty & @Alex_Krause . I’m not certain what a logic converter is, but I’ll take a look through your K40 upgrades.

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Essentially your board takes. 3.3v and the psu 5v.

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It translates the pwm signal from the smoothie to a power level the laser recognizes to get the full use of the pwm

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Thanks again guys. So the “logic converter” is also what people have referred to as a “level shifter”? So simply put, it converts the pwm to a higher voltage level to suit the PSU?

I’d be lost without people like you.

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+Peter van der Walt Thanks for that. I’m not really certain what is going on in those pictures from the scope, but I can at least see that the middle photo (with logic shifter) is more zig-zaggy haha. The other 2 look much more stable. Is the converter that @Alex_Krause suggested suitable? If so, I’ll grab that one.

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@Yuusuf_Sallahuddin_Y ​ on another post of yours I supplied a link to an au retailer that carries the sparkfun Texas Instrument txb0104.

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Those zigzag lines are emf noise in the square wave i believe… and means you have very poor output control of the pwm signal +Peter van der Walt​ please correct me if I’m wrong it’s been ages since I used an O-scope

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@Alex_Krause Thanks for that Alex. I did see you posted that for Susan. I’ll get one from that supplier so I can hopefully be up & running in the near future.

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+Peter van der Walt I’ve ordered one of the SparkFun ones from the link Alex provided in different post of mine. Thanks for your help.

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I have an extra break out board you can have for free if you want it. Just email me ericrihm@gmail.com

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@Eric_Rihm Hi Eric. Is a break out board the same as a middleman board? If so, thanks kindly for your offer, however someone locally in Australia has graciously offered one that they have as an extra also.

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MMMmmm, not sure that I buy that the signals on the scope are telling us anything that bad. My read in order of pictures:

  1. Different scale and horizontal settings than the other pictures, DC scale: 3 divisions @ 100mv = .3v, that does not look right, must be 10x probe = 3.xV as the other pictures are scaled the same?
  2. 0-5V signal, looks like shifting sync due to changing PWM high time (low time is same) which can have many sources including the PWM repeat-ability or simply the sync setup on the scope.
    The only way I can imagine the LS would cause this is if it intermittently changed response characteristics. The LS is pretty passive.
    Unless this LS is weird they are just MOSFETs in series where the gate is controlled by the PS. I suppose supply noise could turn the FETS off… but that would have to be a large PS change.
    The noise levels I see are normal especially if its at the other end of a cable. Doesn’t look like any DC shift on signal assuming the arrow is ground.
  3. Very clean full 3V swing source with no apparent DC offset.

I have done a lot of research on the LPS-PWM interface design. I am inclined to believe that the problem people are seeing in power level are caused by the DC offsets when using the IN port on the LPS and especially when leaving the “Current Regulation” pot installed.
I am also warming up to an open drain approach to this design that does not need a ls. I can’t verify any of this until I get my smoothie setup and test some configurations …
If I use a LS, I plan to use the Adafruit breakout.

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So that is the spark fun LS not the cheapo eBay one.

It is running through a bread board at the moment though.

@donkjr ​ this was my first time using an O-scope and I have no real idea what I’m doing. If I’m being honest. The probe was on 10x, yes.

Do you have advice on settings you would like to see? I have it for a couple more days and would happily hook it up to the various controllers I have.

+Peter van der Walt​ I did hook the Brainz to the laser and just tested power output with similar results. 23-24ma

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At 100% shouldn’t the pwm output be a constant voltage (3.3v or 0v if inverted) anyway unless it has been capped at a lower percentage in the config? I can see flakey hardware potentially introducing some nonlinearity in the power output curve, but at full power I don’t see how it could matter, especially if controlling an enable line instead of the IN line.

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Yes the PWM would be fully high at 100% DF and power at max. However at other DF’s the PWM pulse would be a lot smaller. At 10% DF the PWM pulse would be about 2ms.
I do not know how these various ports would react to higher frequency PWM control. It may be fine but it also could create transient problems in the power output and supply.
When using the IN pin which is an analog input, along with the Current Regulation pot the PWM signal will have a DC offset. If not a problem it will at least create a variable output power dependent on how the PS reacts to the composite PWM-DC signal. In this case I would like to understand how to map the PWM+pot setting to a predictable output power.
Lastly knowing the input characteristics of the PS may allow an open drain interface that does not need a level shifter :).

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+Peter van der Walt There is a native DAC on the LPC1769, you don’t need to add a digipot it’s all there already.
Adding support for it to the laser module is trivial, somebody did it a long time ago but it was never merged ( likely because nobody had use for it )

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Does this mean I can tie into the center tap for my pot input to regulate power?