SoliForum - 3D Printing Community — RAMBo v1.2 and High Temp Readings

Re: RAMBo v1.2 and High Temp Readings

null@example.com (MacGyverX) — Wed, 11 Mar 2015 22:01:46 +0000

I ended up getting another RAMBo (1.2G) directly from the RepRap guys. After flashing it with the same FW I modded before everything worked and detect correctly out of the gate. Even the weird inverted stepper direction issue I had cleared up.

So when something is 30 or more dollars cheaper than the OEM. There is a reason.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (elmoret) — Sun, 08 Mar 2015 01:02:19 +0000

That whole path you described is unfiltered, unregulated +12v from bus 2. It can't be AREF or VCC, since 12v on those would blow the micro controller. I'm not seeing the label in the screenshots you showed?

As far as I can tell, AREF goes from pin 98 on the micro controller to C6, a bypass cap... and nowhere else.

Did you get confused between OVREF and AREF? They are different things - one is an over voltage reference, the other is the reference for the ADC.

I want to understand why shorting that resistor changed anything. Oh well.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (jagowilson) — Sun, 08 Mar 2015 00:59:11 +0000

RUMBA!
http://www.reprapdiscount.com/electroni … v8825.html

You can get it cheaper without DRV8825s, but if you have robustness and repeatability in mind they are good drivers, worth the money.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (MacGyverX) — Sun, 08 Mar 2015 00:46:43 +0000

I've already filled out the RMA request, And it was approved for the return. I don't feel comfy about doing a mod to get the thermistor to work. Last thing I need right now is a fire at the homestead.

Should I get another RAMBo but from another manufacture? (Never heard of Geeetech) Or is there another controller I should look at? I really liked the idea of a software controlled microstepping and trimpot. Makes things easy and repeatable.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (MacGyverX) — Sun, 08 Mar 2015 00:38:17 +0000

https://github.com/ultimachine/RAMBo/bl … /RAMBo.brd

I just realized that its not actually 'geeetech' design. They have a link to that on there wiki.

R73 goes over then pops up thru a via. Then to P$2. To a big ass trace then gets truncated down to a little trace under a cap. Over to a diode then to C40. From there is goes to pin 7 on a LM22675. The label there is 'AREF_VCC'.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (elmoret) — Sun, 08 Mar 2015 00:14:36 +0000

My curiosity has been piqued. Can you link me to the schematic you were looking at?

If your fix works, you should be fine. There's no reason for there to ever be more than 5 volts on those pins unless there's user error, so the protection is a bit overkill (though good design!).

I just want to figure out why your fix works...because looking at the official RAMBO v1.2 schematic, I don't understand.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (MacGyverX) — Sun, 08 Mar 2015 00:09:25 +0000

I grabbed the eagle file from Geeetech. Doesn't matter at this point. I was hopping that was a safe fix. I shouldn't have to do any repairs on a board that less than 10hrs old. So I am going to RMA it and find something else.

Thanks for the help!

Re: RAMBo v1.2 and High Temp Readings

null@example.com (elmoret) — Sun, 08 Mar 2015 00:04:42 +0000

Well I could be misunderstanding something. Was there a typo in your post? R73 is not 200k.

You said R73 is connected to AREF. Where is this on the schematic? I'm not seeing it on a quick glance.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (MacGyverX) — Sat, 07 Mar 2015 23:59:44 +0000

...Great. Back to square one.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (elmoret) — Sat, 07 Mar 2015 23:58:27 +0000

If you shorted R73, I'd expect D12, the over voltage protection zener to immediately blow. I'd also expect you to not have over voltage protection anymore on your inputs.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (MacGyverX) — Sat, 07 Mar 2015 23:54:28 +0000

Amazon

Re: RAMBo v1.2 and High Temp Readings

null@example.com (elmoret) — Sat, 07 Mar 2015 23:54:05 +0000

Where'd you get the board from?

If I'm not mistaken, that resistor is part of the over voltage protection circuit.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (MacGyverX) — Sat, 07 Mar 2015 23:36:34 +0000

Huh. I didn't expect to be doing any surface mount work today. So I looked at the schematic and compared it to the actual board. I noticed R73 200K goes to AREF. I used a Circuit Scribe pen (http://www.electroninks.com/ its for kids- But its so damn handy) to paint over and esscenually short out that resistior. Fired up the board and now it works. Powered it back off. Hit that resistor with a reflow gun and drop a dab of solder on it.

Heh. Pretty crazy.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (elmoret) — Sat, 07 Mar 2015 23:25:07 +0000

MacGyver: You are correct, you don't need to add anything. I was asking you to check that they didn't make a mistake on the board. The thermistor tables expect a 4.7k balancing restistor, IIRC - just as the schematic shows. Is the actual resistor on the board a 4.7k?

Also, is Vcc a steady 5v? Can you measure the voltage between TP20 and ground at a known temperature, say room temperature?

Carl - Read the first post. He already updated to the correct thermistor table.

Re: RAMBo v1.2 and High Temp Readings

null@example.com (carl_m1968) — Sat, 07 Mar 2015 22:49:11 +0000

Would it not be a matter of just changing the thermistor tables in the firmware. I would assume the E3D uses a better quality brand name thermistor than the stock one. If it is different then it's curve will be different and require a different table that is designed for it.