Grounding

9 years 1 week ago #29526129 by Arnott
Grounding was created by Arnott
The HDC2450 user manual says this:

Note6: Beware not to create a path from the ground pins on the I/O connector and the battery’s minus terminal.

Is this a must? Or in high current applications needed but lower power levels it isn’t critical?

Basically we have a lot of other electronics running on the same system battery and some of those signals need to go into the HDC2450. Those signals obviously need a signal common but in this case that is the negative battery terminal.

I can get an isolated supply and run all the other telemetry off it but would rather not do that if I don\'t need to.

Thank you,
Mark

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9 years 5 days ago #29526133 by roboteq
Replied by roboteq on topic Re:Grounding
You cannot the grounding issues given that the same ground is on the power wires as it is on the front connector.

You just need to be careful.

On the power part, beware to never have the ground from the 15-pin connector wired to the - of the battery. If for any reason, the main ground wires get disconnected while high current is drawn, the return current will flow through the 15-pin connector ground. This will burn the wire and pin.

On the signal side, you must be careful that the radio, microcomputer, joystick or other doesnt get its ground directly from the battery. It should take the ground from the 15-pin connector. Otherwise, the serial/radio/analog signal will be extremely noisy to the point it will not work.

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7 years 5 months ago #29528160 by steadirob
Replied by steadirob on topic Re:Grounding
I have a similar problem that has resulted in 2 blown out RF transceivers because:

While the the - pole of the battery is connected to the GND pins of my LDC2250C, that is apparently not the same as the chassis, the metal plate of the motor controller.
When it is all working I measure the full power supply voltage (24 Volts) between the ground pin of the 15/9 pin connector and the metal plate.

At first I though my application of control lights to show the voltage was the cause, but when that is disconnected the same 24 volts is still between metal plate and the ground pins on the controller.

Is this a normal situation? Because the transceivers were grounded to their metal case, they received the full 24 volts on the ground and it burned out .

As it looks now I have to double isolate the controller so it does not touch any part of my - fully metal - system, something that is difficult to do and still has the chance of accidental short circuit.

Please advise, thanks.

Rob

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7 years 5 months ago #29528162 by Griffin Baker
Replied by Griffin Baker on topic Re:Grounding
steadirob wrote:

I have a similar problem that has resulted in 2 blown out RF transceivers because:

While the the - pole of the battery is connected to the GND pins of my LDC2250C, that is apparently not the same as the chassis, the metal plate of the motor controller.
When it is all working I measure the full power supply voltage (24 Volts) between the ground pin of the 15/9 pin connector and the metal plate.

At first I though my application of control lights to show the voltage was the cause, but when that is disconnected the same 24 volts is still between metal plate and the ground pins on the controller.

Is this a normal situation? Because the transceivers were grounded to their metal case, they received the full 24 volts on the ground and it burned out .

As it looks now I have to double isolate the controller so it does not touch any part of my - fully metal - system, something that is difficult to do and still has the chance of accidental short circuit.

Please advise, thanks.

Rob

The bottom plate of the LDC2250 should be anodized and therefore should not make any connections to the gnd terminals.

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7 years 5 months ago #29528168 by steadirob
Replied by steadirob on topic Re:Grounding
The Anodizing has only limited protection: when a screw has made some burring on one of the mounting holes, the full V-bat is apparently on the chassis.

there is room for improvement here.....

I have now isolated the whole unit from the chassis with plastic covered screws and velcro pads underneath the plate.

Still very sad that this - in my opinion not adequate - isolation has cost me almost more in RF-modules than the controller costs....

Otherwise, the system works well.

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7 years 5 months ago #29528169 by roboteq
Replied by roboteq on topic Re:Grounding
The controller does not depend solely on anodization to provide insulation. The PCB has solder mask varnish over the entire bottom surface. In addition, there is an electrically insulating thermal pad under the mosfet area

We have increased our vigilance regarding this question during manufacturing.

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