Hacking the HP45

Powder and inkjet printing
Philipp
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Re: Hacking the HP45

Post by Philipp »

Hello,

Could it be that you've made a measurement error or allocation failure nozzle 4 and nozzle 5?

I try to think without limitations where used to the R10X:
Could the R10X be used to keep the power consumption of the printing head constant?
Could it be used for level measurement of ink?
Could the R10X as pulldown transistors (FET) be used?

It corresponds as any with the nozzles. So the control voltage of the address somehow seems to affect the measurement of R10X and to influence the measurement.

Is there a connection to the driven Primitives?

Best wishes
Philipp
math
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Re: Hacking the HP45

Post by math »

From the datasheet of L6452 seem to me that R10x is used to receive a external current to all nozzle resistors that is provided by the L6452 and is adjusted by an external resistor at pin 93 (Rext) of L6452. This would be used in conjunction with the Rterm of printhead to control the correct temperature of operation of the printhead.
Philipp
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Re: Hacking the HP45

Post by Philipp »

Hallo,
DigitalShadow mentioned on page 5, such a function and relates to one of the HP patents.

If I have understood correctly, the temperature is very important as the point for the release of a drop entscheident depends on the ink temperature. It does initially the enthalpy of vaporization can be achieved and for the starting temperature is crucial. A particularly precise temperature measurement is certainly crucial for a good print.
I have not fully understood how the patent works because of my English is not good enough.

Perhaps someone can explain so that I understand.
Thanks Philipp
Wonko
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Re: Hacking the HP45

Post by Wonko »

"entscheident" -> critical, as in: the temperature is critical for the release of the drop.
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dragonator
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Re: Hacking the HP45

Post by dragonator »

The head is flash vaporizing a tiny droplet of ink. The hotter the fluid is already, the less it needs to be heated. Heating a droplet too much might lead to overheating or excessive wear on the printhead.

Because there is a difference of 13 ohms between the 2 heads I have already, the difference would be at least around 10 degrees Celsius. the 10x can be used to measure the offset. The offset that applies to the 10x also applies to the thermal sense resistor. This offset can be added in the microcontroller to get a more accurate temperature.

The bigger mystery is what the 10x does when an address is high. When I did the measurements a few days ago I noticed the difference and double checked one of the heads. when I have time I will triple check, just to be sure the two heads really are different. I did have connection issues because my carrier warped.
Philipp
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Re: Hacking the HP45

Post by Philipp »

Hello everybody,
thank you for your explanations. I have also understood as you have explained that. However, something is unclear to me how the 10x resistance can describe the offset of the temperature sensor. When the 10x is a discrete resistor which is incorporated in the production, there is no connection between the two components. I think that is not so trivial.

Why should the 10x be as large as 10 heating resistors?
The relationship between thermistor offset and "10 heating resistors" is unclear to me.
The measurements show that the 10x changes when a nozzle is controlled. This perhaps indicates that the 10x is not a single resistor but a merger of the heating resistors, or something similar.

Best wishes
Philipp
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dragonator
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Re: Hacking the HP45

Post by dragonator »

The 10x resistor and the thermal sense resistor are both on the same chip and made in the same process. The thermal sense resistance and 10x resistance are different on both printheads, but when you subtract the 10x resistance from the thermal sense resistance, you get roughly the same number for each head. The value might be different, but the difference between the 10x and the thermal sense is roughly the same. If you measure the 10x value and the thermal sense value, the difference between them gives the current temperature.

The 10x relation to the actual nozzles is also not completely known to me. It might be a handy value to use. It might be several resistors, but the relation itself is very weird to me. I have no idea what the 10x resistance values actually mean, though I am sure it has some meaning.

I double checked the 10x values I got for each address, they are correct the way I posted them. Interesting fact is that the values that are not 300'ish have a higher resistance when I use 5V to trigger the addresses (I forgot to connect the 12V on my first try). This means that 5V is not enough to open the FET gates, and also means that the 10x values run through the comparable (or the same) FET's.
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dragonator
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Re: Hacking the HP45

Post by dragonator »

What has 100 pins and is a disaster to solder by hand. If you guessed porcupine, you guessed wrong, it is the L6452. The short version:

I tried to solder it by hand, I failed. I went to the hackerspace, where they have hot air soldering, smd paste, and all other sorts of tools. I repaired mine, someone else soldered one (the backward one). They both are electrically sound (no shorts, all pins connected). I hope I did not destroy mine by heating it too much, but I can now at least interface with the L6452.

When I will actually do this is still a bit of a mystery. I am first finishing the current circuit design.
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Philipp
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Re: Hacking the HP45

Post by Philipp »

Hello Dragonator,
electronic components have a relatively high deviation from the nominal values. I would imagine that some FETs open at 5V, others have not. Then your measurement results are pure coincidence.
Strange is that you measure a resistor and other components affect the measurement.
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math
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Re: Hacking the HP45

Post by math »

Examining the fig. 1 and the related explanation posted by DigitalShadow on page 5, seem to me that R10X is used only for determine the resistence of heater resistors. Resistence changes with temperature. It's measured the resistence of R10X that are under same temperature of heater resistors. For example, if R10X is 295 ohm so heater resistors are 29.5 ohm. I guess that ten times is for precision and direct conversion. Seem that resistence of heater resistors is importante to calculate energy to send to them.
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