RetireeJay wrote:Are the extruders really that different? What happens if you plug the original extruder (with its thermistor, of course) into the second extruder ports and the second extruder into the original ports? What happens if you use the tuning parameters for the original hot end as the parameters for the second one too?
RetireeJay wrote:The 100k resistor on the third thermistor input should be simulating 25C. Is that what you see on the readout? You could use smaller resistors (all the way down into the range of a few hundred ohms) to simulate higher temperatures. (I don't have any of this hardware, so I can't imagine why the third thermistor is needed.)
RetireeJay wrote:Can you get your scope onto the +12V and the +5V lines on the daughter board? For that matter, can you scope the "ground" voltage on the daughter board relative to the main ground on the Printrboard?
lwalkera wrote:There were some issues I remember Brook telling me with using two different power supplies for the Extrudrboard and the Printrboard. I believe a ground-loop forms which causes the analog values from the thermistor to wildly vary when one of the heaters start up, even though the actual temperature doesn't change. Try using the same power supply for both boards, and/or put a good ground from one power supply to the other.
RetireeJay wrote:This should be easy: Connect your probe ground to Printrboard ground, and then look at the signals on the unused thermistor pins. One of them is ground, and the other is +5V through a resistor - which should be in effect +5V if you have normal 1M or 10M resistance probes.
Tdeagan wrote:RetireeJay wrote:This should be easy: Connect your probe ground to Printrboard ground, and then look at the signals on the unused thermistor pins. One of them is ground, and the other is +5V through a resistor - which should be in effect +5V if you have normal 1M or 10M resistance probes.
Sorry, I clearly drank too much last night (birthday and a bottle of Texas Gin , which, in retrospect is really ironically named 'Genius Gin' )
Are the connections referred to above comparing
- Probe 1 - 12V on extrudrboard
- Probe 2 - 5V on extrudrboard
or (and this is my guess)
- Probe 1 - ground on printrbrboard
- Probe 2 - ground on extrudrboard
- Probe 1 - 12V bed heater on printrboard
- Probe 2 - ground (then) 5V on extrudrboard unused thermistor
RetireeJay wrote:Well, you did the first part the way I meant: one probe on the extruderboard +5V (proxy) and one probe on the main board heater circuit. And you did see a change. Now what lwalkera and I would like to see is one probe on the extruderboard ground (at the thermistor header) and the other probe on the main board heater circuit. To answer the question of whether the 5V is changing all on its own, or does its change merely reflect a change in the extruderboard ground voltage.
lwalkera wrote:You need to connect a heavy wire between both boards, not just connect the two grounds of the power supplies together. On the power supply heating the heatbed, the high current causes a voltage drop across the wire connecting it to the power supply, raising it's ground relative to the power supply which is probably earth grounded through the third pin on the wall cord. When you just connect the grounds of both power supplies together you're not really doing anything since they are connected together though the earth connection in the wall.
All of the mounting holes on both boards are connected to the ground planes on top, bottom, and inside the board. Try running some wire between the mounting holes on both boards.
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