Hacking the HP45

[david]

Regarding the L6452, how did you connect the Vboost pins, i.e. pin 87, 88 and pin 89. The datasheet does not give any clue. regards

[dragonator]

I haven't yet. I am going to as soon as I have the breadboard available. I have also noticed that gap in the datasheet. I think it should be able to run without the VBoost, because what it seems like to me is the regulation pins for a boost converter.

[david]

The L6452 datasheet (p3/22) shows that the transistors used to drive the power line are NMOS FETs, which means they need boost voltage to make high side driving.

[dragonator]

It does indeed seem to be this way. Good call. They are N-Fets, and they have a separate voltage supply. I also cannot find the schematic of the boost circuit. It does seem to be that you can feed an offset voltage yourself. The absolute maximum rating for the V-boost is 28V, suggesting that it expects a separate voltage.

The only thing left to find the schematic out would be to contact ST itself and ask for more information.

On a different note. Fritzing sucks, KiCAD all the way. I have spent a while learning KiCAD and adding all the components I want for the standalone. Just for learning the software I designed a 45x50mm Breakout board with the new connector. While the preparation took a lot longer than with fritzing (me being new and everything), the routing is an order of magnitude more reliable and faster. Never will I use fritzing ever again.

HP45 breakout board V2.01.png (62.42 KiB) Viewed 11533 times

[david]

a little off topic, regardless the capacity of the ink filled, are the HP45 and the HP15 identical cartridge in terms of all other specification?

[dragonator]

A: I do not know exactly. B: They do have the exact same exterior, same PCB design, connector and (I have an empty one by sheer coincidence) on pins 2-12, they do show the exact same resistances, indicating that inside they are roughly the same. I would have to do more test to confirm, but for now I would say they are, if not exactly the same, at least mostly the same.

Also, Adding 3D models to KiCAD is really easy if you primary expertise is 3D design.

HP45 Standalone V0.01 Controller WIP1.png (67.46 KiB) Viewed 11507 times

HP45 Standalone V0.01 Controller WIP2.png (52.92 KiB) Viewed 11507 times

[dragonator]

To fix the issue that I cannot trigger more than 5-6 primitives at a time, I built the entire circuit on a breadboard and used an oscilloscope to probe the circuit. Today I finally had time for this, and I learned squat. Absolutely nothing. Voltages remain stable, timing is fine, no weird noise. There is absolutely no difference whatsoever between firing 5 primitives and firing 14 primitives besides that no ink is coming out of the head.

I will admit that this is a bit of a bummer. I had hoped to find a fix for this, but alas. The standalone controller will be designed with the current hardware, with the limitation that firing in 3 pulses instead of 1 takes over twice as long. That is the next long term goal. Designing and building the standalone controller.

[david]

Forgive my frankness, a breadboard for such high current pulses may not be sufficient. I don't know how you measured the pulses, btw, what's the spec of your scope?

[dragonator]

So far the breadboard and PCB circuit have shown no real difference in inkjet capacity. I am still printing ink perfectly stable through the breadboard. There appear to be no differences between 3 pulse burst mode and 1 pulse burst mode on the scope. I understand what you are trying to say, but 400mA per nozzle is doable on a breadboard, and the roughly 200kHz pulses also are fairly rough. I have seen no ill effects from testing this on a breadboard, though I am not saying that it is impossible.

The biggest problem is that I need to test with a printhead in place, and testing it with a finished circuit leaves me with no real point to hook up testing wires. Putting it on a breadboard and using a direct breakout allows me to probe every pin of the TLC, mosfet and 4017 directly to see what is happening.

I used a Rigol ds1054Z

[david]

I'm really surprised that you didn't see the distortion of the pulses when all 14 channels were fully on. There are couple of reasons,

1. the digital ICs, especially those with registers, do not seem to have decoupling capacitor (unless they are hidden beneath the ICs). The high speed switching may upset the power hence affect the register states;

2. if calculate the 14 channels at 400mA each, it is 5.6A. That is 5.6A pulse at 2us interval, which would cause 11.2V voltage drop on a 1uf capacitor or 1.12V on a 10uf capacitor;

3. the TLC59213 simply won't give you that big current output, check out the diagram on page 5 of the datasheet. unfortunately I just realized it recently, so although I've got the PCB, I won't even try this version.

spd45_1.jpg (130.97 KiB) Viewed 11807 times

spd45_2.jpg (125.44 KiB) Viewed 11807 times

spd45_3.jpg (48.17 KiB) Viewed 11807 times

PS , the rigol 1054 is ok, you can hack it and upgrade to 100MHz or 200MHz I can't remember for sure.