Hacking the HP45

Powder and inkjet printing
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dragonator
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Re: Hacking the HP45

Post by dragonator »

A quick update. I have not been uploading to the forum for a while, there are several reasons.

1. Some things got in the way that kept me busy. This is something between work, a good contest on Instructables and a wedding present that is proving to be quite a handful. The project for contest on Instructables is almost done. The wedding present is coming along nicely, but requires 2 more weeks.

2. The HP45 project had a bit of a stumbling block. The issue was described in a previous post. The MIC5891 chips did a great job driving 12V, but they had 2 issues. They cannot run at 3.3V, so they would already need a level shifter for 3.3V use and they take forever to shut down if they have no load.

The later is the biggest problem. Without some pulldown resistors, the MIC5891 would simply not close in time (taking in the hundreds of microseconds). I tried to add 22 pulldowns to the board, but there simply is no space left. I would either have to widen the board again, or find something else.
HP45 breakout board Oasis test 3.png
HP45 breakout board Oasis test 3.png (203.28 KiB) Viewed 15622 times
The backup plan was the old plan. 3 4017 chips. They cannot run with 3.3V inputs if they run at 12V, so the above mentioned level shifters are required. This is the part that took me so long. Building a good level shifter. I settled on the N-channel mosfet way. It is bi-directional, but I only care about the fact that it works. The initial results are looking good. Floating outputs take 2 microseconds to close. This is more than acceptable.

I still need to test whether it works with the HP45 in place and whether it will work on 3.3V, but it already looks better than the MIC5891. It will take a while before I can pick this project up again, but this is the current status. Also note that I will have my holiday somewhere next month.
IMG_20160711_193322.jpg
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Wonko
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Re: Hacking the HP45

Post by Wonko »

It's great to see some progress again. Fingers crossed.
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Re: Hacking the HP45

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A words only update, no pictures. The way it seems right now, the 4017 connected to the printhead has a shutdown time of 1-2us. This is good, this is what it needs to be. I need some more testing to double check whether the connections to the printhead were sound, but this looks good.

So now I can look ahead a bit further again. I am not going to rush things, I am taking it slow, but these are the tests that I will performing in the coming month or so.
  • Completely rewrite the firmware so it works with the Arduino MEGA 2560 and is a bit more flexible and stable;
  • Transition to the Arduino DUE and test all functions on 3.3V;
  • Add 2 AS6C4008 RAM chips to the circuit and have the inkjet data run through the RAM buffer;
  • Finally redesign the PCB for the inkjet controller and order it;
After that I can resume work on Oasis again.
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dragonator
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Re: Hacking the HP45

Post by dragonator »

2 steps forward, 1 step back.

The 4017 works like a charm while printing, but a small issue was found. The test nozzle function I used to test the condition appears to be broken. I have found it to work less with the MIC5891 test and lowered the threshold voltage so it would work again. I had to lower it to around 2V. With the 4017 I am getting peaks of only 1V. This was a reason for investigation and so I did.

The first test was with the TLC59213 on the addresses. This had a low impedance state when turned off, and I could easily test at a threshold of 3V. I then stepped to the MIC5891, and I had to use pulldowns of 10k or 22k or 33k (I forgot) and I had to lower the threshold to 2V. I though nothing of it at the time, but this has come to bite me now.

Now for the issue. The head has a 63k internal pulldown on the addresses to ground with ground on ground, and 24k with positive on ground. When the 4017 has a pin low, it has a resistance to the ground of 170 ohm. I have 21 unpowered addresses with 24k to the 4017, and 170 ohm to the ground. All power I push through the head while testing seems to be drained to the ground. This is probably why the voltage is no longer rising above 1V. When the capacitor is charged beyond 1V, the resistance to the capacitor becomes so great all remaining current is drained to the ground.

I would do more testing, but I appear to have destroyed my Arduino Mega by putting 12V through a pin. Anyway, I need to find a solution for this. Adding resistors to the 22 pins is not an option.
Danilo
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Re: Hacking the HP45

Post by Danilo »

So happy holidays! When it takes up the idea would certainly more energy ... and maybe some new ideas. :P ;)
Regards, Danilo
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dragonator
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Re: Hacking the HP45

Post by dragonator »

"If it looks stupid but it works, it isn't stupid"
-the Internet

a few days ago I was plagued by a nozzle test function that could not get above 1V, too low for testing. This was because when the ground was closed on the printhead, the voltage was being drained through the internal pulldown resistors of the printhead, through the 4017 output pins (in low impedance state), to the ground of the 4017. This way I could no longer test the nozzles, a dealbreaker.
HP45 Mega connection diagram 5 fault.png
HP45 Mega connection diagram 5 fault.png (476.48 KiB) Viewed 15527 times
The solution is pretty ghetto, but it works like a charm. I added a 2.2k resistor to the ground of the 4017 and 4081. This way, all the voltage that is draining away through the 4017 has the added resistance of the resistor. This way, my voltage is now getting to 3V again. Plenty for testing. The nozzle testing function is working like a charm again, all nozzles that were broken are still broken, so I know the test is working.
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Re: Hacking the HP45

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And this is what the new version of the PCB should look like if nothing changes. I still need to do the 3.3V tests, but right now all components should be able to handle 3.3V, so I am not that worried. The basic changes are this. The whole address side was changed to now have HEF4017 and HCF4081 chips. There are 2 level shifters to shift from the logic (either 5V or 3.3V) to 12V. There is no longer a separate 3.3V and 5V on the address side, saving 1 header via. Also the 4017 require only 2 logic pins, not 3, so this saves another header via. The 2 saved header vias were broken out on the primitive side as aux pins. The resistor mentioned in the previous post is also included on the address side, plus a capacitor to smooth out some noise the resistor was causing.

This whole circuit has already been tested with 5V and works.
HP45 Controller V1.01.png
HP45 Controller V1.01.png (198.56 KiB) Viewed 15518 times
nallar
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Re: Hacking the HP45

Post by nallar »

Did you work out the pinout for the HP23 cartridges?
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Re: Hacking the HP45

Post by dragonator »

Not yet, but I now know how to measure these heads to get a good idea of the pinouts. I first want to get the HP45 working.
bigbomber
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Re: Hacking the HP45

Post by bigbomber »

Hi Dear Friends and specially "Dragonator"

I'm new to this forum but not new to 3D Printing method. I'm Mechateronics Engineer and very interested to Powder Based 3d Printer. Until now I've made a SLA 3d printer (but not using a DLP projector as every one know or a focused point laser) and works on it for 2 years.
At this time I think it is the age of Powder Based 3D Printers. Fast, Cheap and Easy to manufacture and run.
Regards to Dear Dragonator Notes, I've started to drive a HP 45 Head, and got good success. I've Succeed to squirt several Nozzles on first tries.it is very hopeful but at this level it is important for me to drive the Head at correct and best way of possibility (actually I've do some tests on head and the most harmful was putting 24v on Primitive to squirt a nozzle).

As mentioned by Dragonator, the high level pulse width for Fet of each nozzle is about 2 us. To ensure the duration of pulse, I've used a 555 at monostable mode, and just triggering it by each 150 us (actually for 12 kHz we must triggering it by 81 us but best result for me was 150 us).

Also I could not find any good Source Driver IC with t_on & t_off shorter than 5 us in my location, so I've use an open collector driver and put pulses on Return Ground pins :D . By means of at a time one Address and one Primitive is high to 12v (directly), and relative ground pin will be low for 2 us.
It is mentioned it can break the head Fets, and it is because of short pulse width of driving. Actually at 2 us pulses if we use gate of Fets to turn it on or off, during rise and fall times of pulse, a variable resistant will be made by FET and the FET can not handle this amount of Power dissipation and get hot and failed (it is about all FETs and not only for this ink head. This is why at power switching devices engineer try to get frequency lower as possible (under 6 kHz for PWM motor drivers and under 80 kHz for Switching Power Supplies)).

I've also designed my own Head Holder and connector Pins (can't find your accessories in my location) and I will post some photos as they arrived.
I'm good at CAD and CAM and Computer Programming, and I'm glad if I can Help.

And some questions from Dear Dragonator, as you get successfully drive the head, can you exactly guide me about timing pulses and voltage levels?
At my tries, some nozzles work for a while and after a time stop working, and then get work again. And some never works.

From Where you got voltage levels and pulse width?

Also on some tests, a big drop of ink stick to head outlet and disturb ink jetting. what is the reason?

I need to know the exact possible driving timing. I do not want to lose my next Ink Head.

and for last, Dear Dragonator, are you designer and inventor of Plan B?

Regards...
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