TOTAL CONFUSION!! - Possible Programming Issues

Hi peoples,

I started building my very first Prusa Mendel I2 that i had purchased from
amazon [www.amazon.co.uk]
(3rd party dealer) at the start of December. Give or take 3 -4 days later (after work ) I've managed to almost complete it.

HOWEVER, I have spent the past 10 days scratching my head regarding an issue i have with the heat bed. As it describes in the link the heatbed is a PCB MK2a.

Im running ramps 1.4 (red ultimachine??) with a Arduino MEGA 2560 and using the sprinter firmware for pronterface.

I have followed many guides in order to get my prusa mendel i2 completly built as only half of them make any seance.

Anyway the problem i have is that the ramps is not sending the signal to turn on the heat bed (i believe the reason is because that the thermistor is showing 357 degrees Celsius). THAT SAID even the extruder is showing funny temps in pronter face BUT IS still turning on. (151 Celsius - extruder )

The following things i have already checked and double checked are:

Checked power supply from power supply to ramps at 12vdc on both inputs
Checked Resistance of thermistor at 100k
Checked resistance of Heatbed (Is ok but forgotten what it was)
Checked wiring to what ive seen on the guide (http://reprap.org/mediawiki/images/e/e3/Rampswire13.svg)
I have even tried removing the heatbed wires from the output of the ramps (D8) and moved it to D10 (Extruder output) and turned the heatbed on by pressing the extruder heating button in pronterface and it DOES turn on.

So I know the heatbed is working, I know the PSU is capable of the supply for both the extruder and the heatbed 12.03v DC Upto 29 Amps.

So back to pronterface and the software side of things -------

As i said earlier pronterface is receiving funny signals from the thermistors (I have attached a picture) But here is the catch !!! I get these reading with or WITHOUT thermistors pluged in or not

Which points the finger straight at the sprinter software. WHICH i have also had a little play around with.

So when it comes to programming im no genius but i do know my way around a computer. What i tried first was adjusting the config file to a ramps 1.2, Uploaded it, HEATBED WORKED, But nothing else did (properly including the thermistor readings)
I decided to then do a little more research and have a look through the pins page on arduino, I even managed to copy the xyz axis settings of the standard sprinter firmware into the ramps 1.2 definition so that i could use same settings as 1.3 on pronterface.

Gave in with this idea pretty quick as it was still only intermittently working and after all it is a ramps 1.4!! so i went back to the pins page and played around with the following lines numbers:


#define TEMP_0_PIN 2 // MUST USE ANALOG INPUT NUMBERING NOT DIGITAL OUTPUT NUMBERING!!!!!!!!!
#define TEMP_1_PIN 1 // MUST USE ANALOG INPUT NUMBERING NOT DIGITAL OUTPUT NUMBERING!!!!!!!!!
#endif

This seemed to have played around a little with the thermistor readings on pronterface, However as i do not understand programming i am totally oblivious to what i am actually changing .


PLEASE PLEASE PLEASE PLEASE HELP!!!!!!!
I have also tried the marlin software but all the axis are not set up like the sprinters and yet again the heatbed still doesn't work.

Many Thanks
George

Best bet is to switch over to Marlin, it's the more common software to use these days. It has things like auto bed leveling that you might want to use.

There is no reason to play with pins.h on a printer like yours. If you have messed with it, download a fresh copy and use it instead. All of the pin settings are run from configuration.h when you select your main board. That setting must be correct for things to work.

If the thermistors are not reading room temp in Pronterface, there is no reason at all to turn on the heated bed or the hot end. They will not work and they (or the Ramps) can be damaged. Get the firmware reading right first and *then* play with turning things on.

Quick checks:

1) The thermistors need to be wired right and connected to the right pins
2) If the thermistor is unplugged the temp should be something cold (say 0C or below)
3) If the thermistor pins are shorted, the temp should be something hot (say > 300C)
4) At room which the right settings the thermistors should read about 25C +/- 5C.

I had simular problems before I started to get good results. I had the same model and arduino board that you do and I had to reinstall the software mulitple times. Did you put the pin definitions into the Configuration.h part of the programming? If not, that might help you get a little farther with your troubleshooting. This can be found on the [reprap.org] page near the bottom or in the attatched file "for ramps 1.4."

I have attatched a basic readme file I wrote that can help you. This was part of a project that was started as an assignment at the Idaho State University RCET (or robotics) program. You'll need to download the right software and interfaces, if you haven't already, and follow the instructions in the readme file. The file was written for someone who has never done software before, but also included stuff I wish I would have found earlier on in my project. I was unable to attatch the same software and user interfaces that I had found, but I hope that this will point you in the right direction. Let me know if it was helpful or if you need more clarification.
Good Luck!

readme-reprap.docx
ForRAMPS1.4.docx

Hi uncle_bob

Really grateful for your reply, I will take your suggestion of using the marlin firmware sometime in the very near future. However when uploading a fresh copy of BOTH Sprinter and marlin firmwares i still get funny results.

As for wiring i have followed the link that i posted earlier (i.e extruder thermistor goes to point t0 and the bed thermistor goes to t1 )
And also as leading back to point 2 you suggested that pronterface should be reading at 0 degrees, and it doesn't when the thermistors are unplugged so this fault most be to do with the firmware burned onto the arduino mega.

Hi cridreu2

Also really grateful for your response too, However despite this really great information that you provided i still cannot find a solution to my problem. I have ensured that is am using arduino 0023 and have also tried using arduino 0022,

I downloaded my firmware from [github.com]

I have also tried pasting the code that you attached into the pins page under the ramp v1.3 section. which doesn't change the temp reading ATALL however does smooth out the movements a bit (probably will use these setting after these thermistor problems are sorted out )


So Im still a bit stuck lol, but i am terribly greatful that you took you both have taken the time to read this and reply to me.


Thanks
George

Edited 1 time(s). Last edit at 12/29/2013 07:41AM by djtappage.

A few basic things:

Firmware is the code that runs on the Mega hardware. The firmware enables the hardware to do what you want it to. You can have problems with firmware or you can have problems with hardware.

If your thermistors are plugged into the right ports *and* your configuration.h is set up right. You have a hardware issue.

1) With a DVM - what does the voltage on each of your thermistors read at room temperature with everything running?
2) When you unplug the thermistors and check Pronterface, what do the thermistors read?
3) What kind of thermistors (make and model) do you have?
4) What table have you selected for your thermistors in configuration.h?
5) What does the seller have to say about all this?

I had a simular problem when I had the wrong size of thermistor connected in the board. I agree with uncle bob that you should double check which one is selected under configuration.h and see if the manufacturer has any info on it. I also had the same problem shen I was using the right size of thermistor but it was shorted out so the arduino read a very low resistance. My point being, don't rule out the possability of a hardware problem.
good luck!

There are a *lot* of possible combinations and permutations that can create problems....

Thanks for replying again uncle_bob,

When unplugging the thermistors i still get the same reading on pronterface.

Could this possibly mean that the ramp or the arduino mega has shorted.

I have got a DVM and have had it out already to check the resistance of the thermistors, which was reading 100k however i never thought to measure the voltage on them so will do that when i get a bit of time after work.

But surly, with nothing connected to the ramps board i should be getting no readings?? Because atm i am.????

Thanks
George

UPDATE:::


OK so after many hours and weeks i finally worked out the issue and thought i would update this particular forum as SOLVED

There was a EXTREMELY tiny piece of solder shorting out the contact for T1 on the ramps board. HOWEVER after furthur investigation i found that the WHOLE mega board was faulty as i was still getting a reading of 175 degrees on the hotend when i hadn't even turned it on.

So popped on ebay and found a replacedment for £15. Came in 2 days and have just now fitted and now i am getting 22 degrees.!!!


Many thanks for all the help guys and much appreciate it.

Thanks
George