Dear Forum
A Newbie-Question about reading a distance sensor with a CR800. The sensor hast three pins. Vin with 5V/30mA, Ground and Vout (0..3V). I thought I could connect the Vin and Ground with the 5V and G port of the CR800 and the Vout to SE1. But doing so yields to strange behaviour of the logger (communication with PC is lost, the current of the 5V port drops to 4.5 V).
Can anyone guess what might be wrong with this setup? Or is there a better way to connect such a sensor to the CR800.
Thanks in advance for any help
Immediate thoughts are:
1. Sensor is wired incorrectly and you are shorting the 5V of the logger.
2. The sensor draws more than the <200 mA that the 5V can source. (page 40 of the CR800 manual)
Please provide some information about the distance sensor, make and model number.
IslandMan
Thanx for your answer. I am pretty sure, that wiring is correct:
Sensor CR800
Vin------------5V
Gnd------------G
Vout-----------SE1
Power consumption is around 30mA (from technical data sheet and measured by myself).
The sensor is a Sharp GP 2D120J000F.
I was able to locate the data sheet and verify the data.
Can you operate the sensor independent of the logger and verify the correct operation?
I think the problem will be that the sensor is taking big gulps of current as it looks like it uses some for a pulsing technique. The 5V output of the logger is not good at responding to spikes like this, the voltage will sag dramatically during excess demand if the current draw is >200 mA, even for short periods. It is likely any meter you are using is averaging out the spikes of consumption.
There is a warning in the sensor datasheet that points to this: "A 10 μF (or larger) bypass capacitor between VCC and GND near the sensor is recommended." I suggest you follow this advice using a low ESR capacitor of 10 or even 100 μF, either near the sensor or between the 5V terminal and G on the logger.
Thank you very much for this hint, this is very likely the problem. I will test this and finally will report whether it works (in a couple of weeks).