Some question about MLX90614
paolo grigioni
Posts: 15
Hi,
two years ago I bought from parallax some MLX90614 90° FOV.
Recently I've substituted the IR sensors on the boards with the 10° FOV model.
1st Question: there is something to take into account in the parameters setting after such operation?
All the three sensors seems to work well (they are driven by a BS2P) but reading their eeprom parameters appear something that I don't understand.
When I ask for Config register bytes, all sensors give me the following binary value
1011011111110000
Following datasheet (table 7 on page 12) its meaning is
bit 0-2 000 IIR Filter=50%
bit 3 0 Repeat sensor test OFF
bit 4-5 11 Tobj1, Tobj2
bit 6 1 Dual sensor IR
bit 7 1 Negative sign of Ks
bit 8-10 111 FIR Filter=1024
bit 11-13 110 GAIN=100
bit 14 0 Positive sign of Kt2
bit 15 1 Disable Sensor test
2nd Question: Why They seem to be Dual sensors (bit 6) and the readings are for TObj1 and Tobj2? Do I have to change these values in order to make sensor working propery?
thanks
Paolo
two years ago I bought from parallax some MLX90614 90° FOV.
Recently I've substituted the IR sensors on the boards with the 10° FOV model.
1st Question: there is something to take into account in the parameters setting after such operation?
All the three sensors seems to work well (they are driven by a BS2P) but reading their eeprom parameters appear something that I don't understand.
When I ask for Config register bytes, all sensors give me the following binary value
1011011111110000
Following datasheet (table 7 on page 12) its meaning is
bit 0-2 000 IIR Filter=50%
bit 3 0 Repeat sensor test OFF
bit 4-5 11 Tobj1, Tobj2
bit 6 1 Dual sensor IR
bit 7 1 Negative sign of Ks
bit 8-10 111 FIR Filter=1024
bit 11-13 110 GAIN=100
bit 14 0 Positive sign of Kt2
bit 15 1 Disable Sensor test
2nd Question: Why They seem to be Dual sensors (bit 6) and the readings are for TObj1 and Tobj2? Do I have to change these values in order to make sensor working propery?
thanks
Paolo
Comments
I've changed that unusual values, but I've another question for you all:
On datasheet there are only some RAM & ROM location explained, is there someone who has the complete map of both RAM & ROM with their meaning?
I hope to received at least 1 answer!
Paolo
Now I've another question.
I put a standard servo between two MLX90614 to make IR Temperature measures with and without a filter. It seems running well but looking at the internal MLX Temperature I've found a lot of jumps (all about 1 °C sometimes up and sometimes down)! I think that behaviour is related to servo always powered: is there a way to turn off the power on servo connectors once the servo has reached the needed position?
I'm using a BOE USB with a BS2P. Could you suugest me the right FET to use and the correct way to use it? I'm not so expert about them!
thanks
Hi Paolo,
My first reaction to your graph is that your part has a dead ADC bit. Using your "about 1 degree C" number and knowing the resolution you might be able to determine which bit. I'm guessing most likely the MLX90614 has a stuck bit, next likely the SW driver and least the IC2 translation device. To isolate it you might be able to set up an established temperature near the trip point and watch the serial data into and out of the translation part with a scope. VERY slowly raise the temp and look for the bits to count up (just like they did in Matrix). At the bad spot it should count backwards that bit amount and then continue counting up again. These part are still available from DigiKey-Melexis.
Or at least that's how I'd approach it. I'm curious about how you're doing with this board.
Dom...