Hacking the HP45

[david]

Driver output at 12kHz ...

[david]

It worked, very preliminary. I don't know which nozzle is ok which not. I tested with 0xaa and 0x55 sort of pattern. I'll do more test and clean up the design. A two layer PCB is so difficult to route for this board. I'll probably use a four-layer board in next version.

PS those drops were so fine. They were more like mist or smoke instead of drops. And interestingly, you could hear the 12kHz noise from the printhead.

[dragonator]

That looks amazing. The ink stream does indeed look more like a fine mist. You wouldn't think it was an image until you hold the head a few millimeters from the paper. Considering your board size and what is on it, I am already amazed that you managed to fit everything you did on a 2 layer board. My design is on 2 40x90mm boards. The head does indeed produce a nice sound when it is printing. Based on the volume you can hear how many nozzles are on.

When you can I would be interested to see the schematics of at least the inkjet part. While I will not use the L6452 right now (I am already in the process of ordering my current design) I do want to experiment with it in the near future. My V2 driver board might be designed around the L6452 if I know how it works.

[david]

The current problem is that the driver might be too powerful. Depends on the settings, the driver can boil the printhead in just seconds, where it stops jetting but you can hear the sizzling sound in the printhead, after a bit cool down it can print again, a lot more robust than I thought.

I'm pushing the edge of the 2layer PCB, I've just done some update and luckily I could still fit everything with 2 layers. So it will still be two layer PCB for next version.

Another advantage is that with this driver it can print with power supply from 19V to 24V.

BTW, the PCB shown in the above picture is not the driver PCB, it's an interface PCB that can connect a PC to the driver. The driver PCB has already installed at the back of the cartridge carrier.

[dragonator]

Do you have the ability to lower the primitive voltage in any way? Seems to me like you are putting too much power in the head. With the TLC circuit i doubt that I am getting power and I also am only on 1/3rd duty cycle. You seem to be printing on full speed, with full power.

I am aware that the PCB shown is your interface board. You have shown that a few pages back.

What did you do with the Vboost of the L6452 in the end? All other pins in the datasheet I can place, but those are still unclear to me and obviously you did something right there.

[david]

My driver has been designed to do full power full speed. There is an on board programmable 4A DC-DC converter can output 5V to 13.5V. The interface was supposed to connect upto 5 printheads (with own slave version of the driver) by just one long cable, and they could be chained by short local cable.

The DMOS driving power pin is actually called Vsetup in the L6452 datasheet, probably I first misleadingly called it Vboost. But the boost (two pins next to the Vsetup) on L6452 seems something different which I still hasn't figured out. I think Vsetup needs to be 11V above Vh, I'm still testing this part.

Also, a bit off-topic, any idea how the colour version HP78 works? since it is narrower, I guess it can't print with the black at the same time and may need a second pass for printing the colour.

PS, there are always some hi-tech companies afraid of customers knowing how to use their products.

[dragonator]

That is enough for me to work with. I am done with the breadboard, so I can also start testing on the L6452. Does it accept 3.3V logic? The datasheet seems to suggest so, but it is a bit on the limit (0.667x5V=3.335V).

The HP78 to my knowledge works the same as the HP45, only with around 100 (96?) nozzles per color for 3 colors. The swatch size is smaller than on the HP45. I have been told that the color heads are more fragile. Wrong timing will destroy nozzles earlier and there is a tiny metal plate that can detach and ruin the head. I have not yet worked with the full color ones. There is also HP45 sized heads that have a single color if I am not mistaken.

CFconn is also a bit fussy about their connector design. They have shared enough for me to work with, but 3D cad they won't share and they have asked me not to publish too much.

[Mahsa]

hi hp45 hackers. first tnx for your information i read all of them.thats great. and then david i think v boost need some pulse to recharge the storing energy.there is a mosfet inside it.by a pulse it will be on.

[davidk]

Dragonator, on your design, did you try with two TLC pons parralelled? On my math it should provide enough current for firing all 14 nozzles.

[dragonator]

Not on this version. I do have 3 on it because I could fit that without much modification. With 3 I can run with 2 pulses. I am going to try to night on the breadboard, but I suspect that if I get the L6452 to work that V2 will not have any TLC59213's at all.