Smart Implant with voltage divider circuit

[wclarke 0]

I just purchased the Smart Implant with the goal of monitoring my solar battery voltage.   I've made some attempts to get the circuit working with no success, so I'm here to ask for help.

 

The battery is 48v, voltage ranges from 48v to 54v.

I have been trying to setup two voltage divider circuits;

one to power the Implant (9-30V),

another to drop the battery voltage down for the Implant to connect to In2 to monitor the voltage (0-10v).

 

See my wiring diagram below.  Does this make sense?   

Any help you can offer would be greatly appreciated.

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[Martin_N 154]

@wclarke

Hi.
I had to recalculate, but it looks like the voltage divider is fine. Personally, I would use a step-down DC/DC converter to power the SI.
So the only question is how you have configured the SI. It should be without pull-up resistors. According to the manual, this corresponds to a 3-wire connection.
Another warning. You get a voltage update at a maximum rate of 1x per 30 seconds. You won't get a shorter time. So the question is whether you were able to wait long enough when connecting for the first time before you started looking for a "bug".

 

eM.

[wclarke 0]

Thank you for responding Martin  @Martin_N

 

This morning I have double checked my wiring and voltages per my diagram and the divider circuits are working properly.   The issue i have is when I connect the SI power wire, the voltage on that divider goes from 16v+ down to 4.8v.   Something in the SI is causing the voltage to drop and too low to power the SI.   I'm researching this now and seems to be a "load drop" based on the resistance in the SI.   

I'm working with a little breadboard kit I had on hand, so I have limited resources at the moment.   

[Martin_N 154]

@wclarke

How do you set Smart Implant? Send a screenshot.

[wclarke 0]

I'm using Universal Devices' EISY hub.   I've set parameters 20 and 21 to value of 4.   Is this correct?

Unfortunately this hub does not have a way to display all parameters of a node, I have to individually query each one.

When adding the SI to this hub, it creates a bunch of devices: (ZY 089 is the SI).

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[Martin_N 154]

@wclarke

Yes, parameter 4 is correct - analog input without internal pull-up resistors.

 

If you solve the problem with the load on the voltage divider (probably it is the internal design of the SI and its internal resistance). I suggested solving this with the help of a stepdown converter.

 

If I calculated correctly, the change between 54 and 48V means a change of about 1V on the voltage divider. In this case, it is two steps (default setting). So if you have a solved power supply, pay attention to this issue, see the manual:

 

 63. Analog inputs - minimal change to report

This parameter defines minimal change (from the last reported) of analog input value that results in sending new report. Parameter is relevant only for analog inputs (parameter 20 or 21 set to 4 or 5).

Parameter size: 1B

Default value: 5 (0.5V)

Available values:

0 – reporting on change disabled

1-100 (0.1-10V, 0.1V step)

[wclarke 0]

@Martin_N

Thank you Martin.   

Seems to be working at the moment.   I couldn't figure out the voltage drop on the SI power side, so I'm using a small 12v charger.

I confirmed parameters 20, 21, and 63.

All good.   Thanks for your help.

 

[Tim__ 126]

A resistor divider to provide the input power will not be reliable, as the voltage will vary based on the current used. Use a DC to DC converter like this one  

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