Hacking the HP45

[dragonator]

Looking good.

I like the idea of the analog maximum pulse width. Do you have any way of lengthening or shortening it in the future to modify it?

Switching regulators should not give massive amounts of problems for the micro's. The bigger problem is the massive spikes in required current from the head, but that is something that a big capacitor should be able to fix. micro's should be fine handling the tenths of volt spikes of a regulator.

[bigbomber]

I like the idea of the analog maximum pulse width. Do you have any way of lengthening or shortening it in the future to modify it?

Hi
pulse width is a constant, there is no need to change it during a process, but if you mean change it in next version of driver, I can say YES. By changing a simple resistor or a capacitor, I can change pulse width.

[jnesselr]

I like the idea of the analog maximum pulse width. Do you have any way of lengthening or shortening it in the future to modify it?

Hi
pulse width is a constant, there is no need to change it during a process, but if you mean change it in next version of driver, I can say YES. By changing a simple resistor or a capacitor, I can change pulse width.

You would want to change the pulse width programmatically depending on the temperature of the head. If I do understand this correctly, and the inkjet head is current activated, then it needs a certain amount of current for a certain time to actually fire the nozzle. If the current source and voltage is constant, then the only thing you would modify based on the temperature of the print head is time. I believe that the hotter the nozzle is, the less time it requires to fire overall.

[dragonator]

Because this circuit is now in the hands of more people, I have been asked to give the lists. Because I cannot work on this for a little while longer, I have made these lists. This includes a component list and a schematic. I tried my best to check for errors, but I cannot give any guarantees until I myself have made another circuit with the schematics.

Male and female headers are not included in the BOM for "Fritzing is not perfect" reasons. The pogo pin used is: "0.8mm Dia Spherical Tip Spring Loaded Test Probe Pin". The only important thing of the pins is that the barrel diameter is smaller than roughly 0.8mm (0.7 to 0.6mm). This is the page I bought them from, though it currently says last one:

http://www.ebay.com/itm/231497396915

HP45 Controller Schematic V1.01 schematic.png (373.33 KiB) Viewed 14966 times

HP45 controller V1.01pinout.png (108.86 KiB) Viewed 14966 times

V1.01 controller bill of material.xlsx.zip

(7.06 KiB) Downloaded 787 times

[dragonator]

Mistakes were made in the BOM. I repaired what I could. Main changes:

• 1. is now 2.2k. There are now 5 2.2k resistors instead of 4.
• IC8 was the HCF 4081. It is now renamed so it is correct.
• IC5-7 were long and tedious numbers. They are now what they really are. HCF4017.

As for the 4081 and the 4017. Any type of these chips is acceptable as long as they can handle up to 12V.

The attached file can be opened in any web browser. It is a raw fritzing output in html. Excel will come with later updates.

[dragonator]

The last thing I missed was a carrier for the new controller.

I first tried to improve my old design. It does work really well, but it is may different pieces. The new design I made only had one piece. That would have been great, if it had actually worked. It is also a tolerance problem, but for now I am sticking to the old design.

So I modified the hole pattern so it matches the controller and 3D printed a new carrier in glorious green PETG. Checking hole alignment by eye is near impossible, but it should be pretty close. In the coming weekend I hope to test it. I have also started looking into Python so I can slowly start on a image to inkjet conversion. I am aware that there have been people how have already done stuff like that, even on this forum, so I will also look into that.

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[jnesselr]

If you can help me get a working assembled board to test, I can definitely help on the code side. I haven't even gotten ink out yet though.

[dragonator]

I have to order basically all important parts before I can ship out working HP45 controllers, but as soon as this thing is tested and works well enough I will take you up on that offer.

[evomotors]

@dragonator - Can you share the PCB design files so I can order some PCBs to play around? I would also like to get the STL file for the cartridge holder.
Thanks in advance.

[dragonator]

At this very moment I am working on the controller. I hope to have an "all nozzles are on" before the end of this weekend. After that I will share the PCB and the stl. I first want to be sure this thing actually works. For instance I had some issues with the carrier not alighting properly. I am currently making a new carrier that can be adjusted so I can make the pogo pins line up. All systems by themselves are working. I only need to get them all to work at the same time.

If you want I can also send you one or two PCB's. Flat rate is less than €5 worldwide.