Hacking the HP45

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dragonator
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Re: Hacking the HP45

Post by dragonator »

The VHEAD is an option for the future. Officially, the HP45 has a variable voltage on the primitives. Depending on the type of ink, state of the head, and environmental factors, the voltage required to fire a primitive is variable. On the C8855 controller there is a variable voltage available.

The printhead tests the optimum voltage by firing all nozzles for x amount of times and measuring the temperature rise. It does this test for a range of voltages from around 7V to 13V. The voltage at which the temperature rises the least is the ideal temperature. A higher voltage and the head is still on after the droplet has been ejected. A lower voltage and the head does not properly eject a droplet, keeping all the heat inside the head and not in a droplet.

Current controllers lack this option, but I do have an extra input in the way of the VHEAD pin. It is currently connected through the solder jumper, but disconnect that jumper and you can input a separate and variable voltage to control the head.

rofl
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Re: Hacking the HP45

Post by rofl »

Thanks for reply.

I am also having some difficulties testing the head. When I connect it, I noticed that connection is quite unstable, i.e. sometimes temperature shows -0.2, but when I push it really hard, it shows ~25-30. Rarely, I manage to test the head and it shows 300/300, temperature also is shown like ~30, but when I try to prime it, i.e. spray some ink, nothing really happens. Do you have any ideas why? I have attached image, where I see that some pins do not hit the connection pads right in the center, do they have to hit it in the center?

Also I noticed that main voltage regulator and IC5, IC1 get really hot. I can hold my finger for a while, but after a while it is quite hard to do that. Is it normal?

I also noticed that when it does not show temperature, it tests 300/300, when temperature is displayed, it always tests 0/300..

Thanks.
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Re: Hacking the HP45

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If the head only shows a temperature when you push it really hard, the carrier you printed is wrong. Probably the pins do not protrude far enough out to properly contact the printhead. If the temperature shows, it is an indication that some pins are connected, but you only need 3-4 pins to connect correctly for the temperature to show up. The pins do not have to hit in the center, but every single pin has to contact the printhead, or something will not happen when you try to print (no temperature, or missing nozzles).

IC5 and IC1 should never be getting hot. The fact that they do indicates a short or a bad component somewhere. Do these components also get hot when there is no printhead connected. If so, there might be a short somewhere on the board. The voltage regulator can actually get a bit hot. It goes from 12V to 5V and dissipates the excess.

For the priming of the head, you should first try actually cleaning the printhead with a damp towel before use. Older heads have a hard time starting up.

The temperature not showing when it tests fine is odd. Given the possibility of a short on the board it might be explained, but that seems weird.

rofl
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Re: Hacking the HP45

Post by rofl »

I will work this evening with some ideas. I will let you know the results. I am very greatful for your help.

By the way, HP connector tends to bend a bit when fixed on PCB. Springs lift its sides a bit. I hope that does not affect connection severely. See image. I did not overscrew it. Screws are just barely screwed.
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Re: Hacking the HP45

Post by dragonator »

The bending of the connector is normal. The mounting holes are in the middle, and the springs on the side, so it is bound to happen. The springs usually compensate for this. One question. Do you have gold plated PCB or, tin plated?

rofl
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Re: Hacking the HP45

Post by rofl »

Good question, but I have gold plated. These were, obviously, way more expensive as well. I finished reprinting parts with FDM (older ones were SLA made), so I will give it a try later. By the way, I used parts from source package, not the make package as I was not able to see any difference. Are there any differences between source and make files of head mount?

Oasis make package 20181230
Oasis source package 20181014

Thanks

rofl
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Re: Hacking the HP45

Post by rofl »

Well, with reprinted FDM parts it seems that connections looks better. At least temp is displayed all the time. Also, when I touch the end, it increases, so some kind of response is observed. However, this time, it does not test the head. When I test it, it shows 0/300, which is not that good.

I bought another HP head to eliminate potential risk of having flawed head (it should come tomorrow or so). But right now, I see that ICs are not that hot. They are warm, but not that hot as before.

Do you have any ideas, how to test if connection is good enough?

P.S. I have red all 60 pages of this discussion a couple of months ago, so I might not remember everything if it was mentioned before, sorry.

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Re: Hacking the HP45

Post by dragonator »

At this point I am worried that either IC1 or IC5 has failed. The fact that both got hot is a bad sign. Either can stop the address side control from working.

2 manual override commands that might help you. "ANX" is address next. It simply goes to the next address. "ARS" is address reset. It puts the address back at -1. Both can be given over the Arduino Serial command line.

http://ytec3d.com/wp-content/uploads/20 ... acts-5.jpg

Take a multimeter, attach ground to the ground input of the controller, and find address 0 on the link above (your contacts will be mirrored because the image is for the head, not the connector). Give "ARS" over serial. Measure A0, give "ANX" and measure it again. It should be 12V. Every ANX will bring you to the next address.

With a schematic and a few breadboard wires you can probe the controller by itself, but that requires a bit of knowledge on electronics.

Lastly you can actually try to replace IC1 and IC5, assuming they actually are broken, but that is a bit of a wild guess.

I would love to give something easier to measure, but measuring a controller is still too difficult. It is on the list to add self testing abilities, but HP45 work is a bit on the back burner.

P.S. Impressive work reading all that. This page has grown a bit out of hand over the past few years.

rofl
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Re: Hacking the HP45

Post by rofl »

Oh and by the way. Do you think that flawed HP45 head can damage controller? I was just thinking, how to approach further steps if my current head is somewhat damaged. If something is shorted, is there a chance that controller will not handle that and cause damage tos ICs etc?

I will solder 2nd controller from scratch tomorrow or a bit later. I have parts for 3-4 of them (except teensy and hp connector which I have just one of each). So if HP45 cannot damage controller I would try new jet head with my current controller before attempting to test in on newly soldered.

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Re: Hacking the HP45

Post by dragonator »

A poorly connected head might, but even that would be bad luck. A bad head should not be able to damage the controller. A printhead is filled with fragile heater resistors that will break in such a way that they no longer conduct. A non-conducting heater resistor will not do anything bad to the controller.

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