I know this is not the answer, but IIRC RS (RadioSpares) has a dedicated
print head controller IC. I guess you have checked the manufactureres site
(I hope they have one) to see how they recommend to do it ?

I prefer the electro thermal system, seemed easier to use :o)

Regards,

Kat.
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----- Original Message -----
From: "David VanHorn" <dvanhorn@CEDAR.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, November 08, 2001 4:29 AM
Subject: A printing conundrum


> This is a generic question.
>
> I'm trying to wrap my head around thermal line printing, and I'm not
seeing
> my way through the main printing operation.
>
> In order to print, I have to load the head with data, fire six print
> pulses, and step the motor.
> If I didn't care about speed, I would simply do this all in sequence, and
> be done with it.
>
> However, I do.
>
> So:
>
> I can load the head during the burn time, which is nice.
>
> My conundrum comes down to how to resolve the situation where the sum of
> the burn times may exceed the normal time between motor steps.
>
> Normally, I can complete all six burn pulses in less time than a motor
> step, so the obvious method would be to use a timer as a lockout, saying
> "you can't step the motor till I expire".
> In fact, it's very tempting to run the motor on a timer interrupt.
>
> However, as the temperature and battery voltage drops, the burn time
> increases, and I may not be able to complete all six burns before the
timer
> expires.
>
> The first order solution seems to be to step the motor when burn is
> completed and timer expires, but that seems to have a problem too.  If the
> motor is accelerated to some value, and I hit a "thick patch", then I'm
> likely to show down significantly, and the motor may not be able to track
> the change in speed. Also, on the other side, I may come out of a "thick
> patch" and need to accelerate rapidly.
>
> Additionally, I have to compensate for residual heat in the printing
> elements, so I have to alter the burn time dynamically, in response to the
> printed data as well.
>
> The problem seems deceptively simple at first, but the more I look at it,
> the more interesting it gets.
>
>
> Has anyone on the list worked through this before?
> Am I walking into a deep hole here?
> :)
>
> --
> Dave's Engineering Page: http://www.dvanhorn.org
>
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with
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>
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>
>

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