Proper Voltage for the ULN Outputs

[Builder123]

Are the outputs for the ULNs all supposed to be greater than 20 volts? When I apply 24v DC power to the protoshield (without it connected to the Arduino), I get 22.3 volts at all 12 outputs on the ULNs. However, when I connect the protoshield to the Arduino Mega and apply power to both the mega and protoshield, the voltage drops to .15volts for 9 of the ULN outputs and 22.3 volts for the other 3 outputs. The ink cartridge was semi operable in this condition but appeared that ink was not spraying from all nozzles. Now I believe the cartridge was damaged as it is no longer spraying any ink.

So my question is, are all 12 outputs from the darlington arrays supposed to have 20+ volts? Also, where are you grounding pin 8 on both darlingtons? Currently I have these two pins connected to the circuit (as shown in the schematic), but not grounded in another place as the schematic suggests. When I connect these pins to the ground from the 24v power source (which is connected to the ground from the Arduino power source), I get voltages of 10+ volts at each of the ULN outputs... does this seem right?

Appreciate the project and assistance.

[Pwdr]

The Arduino shouldn't need a separate power source, it can run from the USB voltage fine. The protoshield should have a separate supply and should not be connected to any power from the arduino board, but off course the ground should be connected.

When the boards are connected correctly, the ULN's should have all ±22V on them.

On Tuesday, February 26, 2013 at 02:36 , Builder123 wrote:

Are the outputs for the ULNs all supposed to be greater than 20 volts? When I apply 24v DC power to the protoshield (without it connected to the Arduino), I get 22.3 volts at all 12 outputs on the ULNs. However, when I connect the protoshield to the Arduino Mega and apply power to both the mega and protoshield, the voltage drops to .15volts for 9 of the ULN outputs and 22.3 volts for the other 3 outputs. The ink cartridge was semi operable in this condition but appeared that ink was not spraying from all nozzles. Now I believe the cartridge was damaged as it is no longer spraying any ink.
So my question is, are all 12 outputs from the darlington arrays supposed to have 20+ volts? Also, where are you grounding pin 8 on both darlingtons? Currently I have these two pins connected to the circuit (as shown in the schematic), but not grounded in another place as the schematic suggests. When I connect these pins to the ground from the 24v power source (which is connected to the ground from the Arduino power source), I get voltages of 10+ volts at each of the ULN outputs... does this seem right?
Appreciate the project and assistance.

—
Reply to this email directly or view it on GitHub (#19).

[digitalw00t]

The only time you should have to mess with that is if you are printing from
an sd card, then you might need one if you wish to disconnect and walk away
with your computer.

On Tue, Feb 26, 2013 at 2:00 AM, Pwdr notifications@github.com wrote:

The Arduino shouldn't need a separate power source, it can run from the
USB voltage fine. The protoshield should have a separate supply and should
not be connected to any power from the arduino board, but off course the
ground should be connected.

When the boards are connected correctly, the ULN's should have all ±22V on
them.

On Tuesday, February 26, 2013 at 02:36 , Builder123 wrote:

Are the outputs for the ULNs all supposed to be greater than 20 volts?
When I apply 24v DC power to the protoshield (without it connected to the
Arduino), I get 22.3 volts at all 12 outputs on the ULNs. However, when I
connect the protoshield to the Arduino Mega and apply power to both the
mega and protoshield, the voltage drops to .15volts for 9 of the ULN
outputs and 22.3 volts for the other 3 outputs. The ink cartridge was semi
operable in this condition but appeared that ink was not spraying from all
nozzles. Now I believe the cartridge was damaged as it is no longer
spraying any ink.
So my question is, are all 12 outputs from the darlington arrays
supposed to have 20+ volts? Also, where are you grounding pin 8 on both
darlingtons? Currently I have these two pins connected to the circuit (as
shown in the schematic), but not grounded in another place as the schematic
suggests. When I connect these pins to the ground from the 24v power source
(which is connected to the ground from the Arduino power source), I get
voltages of 10+ volts at each of the ULN outputs... does this seem right?
Appreciate the project and assistance.

—
Reply to this email directly or view it on GitHub (
#19).

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/19#issuecomment-14099942
.

./Andrew

[Pwdr]

As mentioned in a different issue, the Arduino reboots when the connection is made or broken (at least when connected to a Mac)

On Tuesday, February 26, 2013 at 09:02 , Andrew Falgout wrote:

The only time you should have to mess with that is if you are printing from
an sd card, then you might need one if you wish to disconnect and walk away
with your computer.

On Tue, Feb 26, 2013 at 2:00 AM, Pwdr <notifications@github.com (mailto:notifications@github.com)> wrote:

The Arduino shouldn't need a separate power source, it can run from the
USB voltage fine. The protoshield should have a separate supply and should
not be connected to any power from the arduino board, but off course the
ground should be connected.

When the boards are connected correctly, the ULN's should have all ±22V on
them.

On Tuesday, February 26, 2013 at 02:36 , Builder123 wrote:

Are the outputs for the ULNs all supposed to be greater than 20 volts?
When I apply 24v DC power to the protoshield (without it connected to the
Arduino), I get 22.3 volts at all 12 outputs on the ULNs. However, when I
connect the protoshield to the Arduino Mega and apply power to both the
mega and protoshield, the voltage drops to .15volts for 9 of the ULN
outputs and 22.3 volts for the other 3 outputs. The ink cartridge was semi
operable in this condition but appeared that ink was not spraying from all
nozzles. Now I believe the cartridge was damaged as it is no longer
spraying any ink.
So my question is, are all 12 outputs from the darlington arrays
supposed to have 20+ volts? Also, where are you grounding pin 8 on both
darlingtons? Currently I have these two pins connected to the circuit (as
shown in the schematic), but not grounded in another place as the schematic
suggests. When I connect these pins to the ground from the 24v power source
(which is connected to the ground from the Arduino power source), I get
voltages of 10+ volts at each of the ULN outputs... does this seem right?
Appreciate the project and assistance.

—
Reply to this email directly or view it on GitHub (
#19).

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/19#issuecomment-14099942
.

./Andrew

—
Reply to this email directly or view it on GitHub (#19 (comment)).

[Builder123]

Thank you for the assistance. Turns out my cartridge was bad.