I need help with the design of a timer delay circuit for the output of a sensor circuit which can keep the output HIGH for an adjustable time range (about 1 to 10 min), after the digital output of the sensor circuit goes LOW. Also, the timer should be restarted automatically if the output of the sensor circuit goes HIGH again in the middle of the timer operation.
I saw many different power off delay timer circuits which used the 555 IC, for example, this circuit, but I can't find a resettable timer circuit.
More details: in my case the sensor circuit is a temperature circuit with a si50 sensor: http://www.kynix.com/Parts/2540249/SI7050-A20-IM.html and after it triggered on adjusted temperature, the output went HIGH (12V) and if the temperature suddenly drops below the trigger point, the output will go LOW as well(it contains hysteresis). I need a time delay after the output of the temperature circuit in order to keep the output HIGH for the adjusted time range, and, if the output of the sensor circuit goes HIGH again, the timer interval's must be restarted and it must wait until the signal goes LOW again(like in the motion sensors's delay circuit which id active while it's sensing motion)
-I know it is easy to do it with a microcontroller but I still need to learn more programming .
-It's not possible for me to learn programming at the moment ,so maybe a retriggerable monostable is what I want ?
Below is diagram of the temp. sensor:
schematic according to RoyC answer:
I have a PCB built with SI7006 placed on 4x6cm board, with other heat sources (MCU, radio), and I need a method to compensate the temperature to find the Ambient Temperature.
I read the Application Note AN607 and AN1026; the last one has some mathematical laws that I am trying to apply.
Page 4: estimating the System Temperature, I don't clearly understand what's exactly delta_T0, T1. I've measured in my system (with an IR thermometer):
* the biggest temperature on the PCB (next to a MCU) ~35 deg C.
* SI7006 indicates 32 deg C
* the PCB next to SI7006 is 32 deg C
* Ambient temperature is 25.7deg C
* this situation stabilised after ~30 mins (1800 sec) startup
So, I've used:
t-t0 = 1800
Time constant T = 83 sec (as PCB is made from FR4, computed on the previous page)
delta_to = 32 - 25.7 = 6.7; I know initially the sensor measured exactly 25.7 deg as Ambient_T
With this data the result delta_T is 32; which doesn't make sense, as T_ambient is 25.7.
The formulas used are: delta_T= delta_T0+(T1-delta_T0)*(1-exp((t0-t)/T))
T_system =T_ambient + delta_T
So, what's the mistake?
Hello, I'm not so familiar with the SI 1133 and don't understand the measurement procedure completely.
I want to use the SI 1133 as light sensor for a pulse oximeter. Therefor I must measure the intensity changes over the time (for example 5 or 10 minutes).
I don’t understand what the sensor gives me back as result of the measurement. Is it just one number? Because the HOSTOUT register is 8 bit long, but you can change between a 16 or 24 bit long measurement? And how is the result related to the light intensity?
I also don’t really understand the function of the measurement time (HW_GAIN) and the number of measurements (SW_GAIN). Does it mean I can do 128 measures in 24.4µs? And how can I distinguish the 128 measurements?
I hope it is clear what my problems are, and I hope somebody can help me.
Thank you a lot
I wanted to know is there any demo / example code available to read the Si7021 sensor temperature and humidity values which on the EFR32MG12 Mighty Gecko Kit. How to communicate to this sensor?
I want to use four SI1133 Senors at the same time. To get the data from all four Sensors I think I have to change the slave address off each sensor right? I read in the Data sheet that it is possible but I don't know how it works.
Are there any examples how to initialize the SI 1133 or some kind of User Guide?
I am looking for AC current sensor of small form factor and less than $1 per unit. My agenda is not to do accurate current measurement but to know whether the current is following through the PCB trace or not to identify whether the particular appliance is on or off.
Si8512 seems to be a good option but it has reached EOL. Please suggest an alternate part for the same. I am considering ACS712, but is there any offering from Silicon Labs?
I have attached the schematic in which the I need to know whether the current is flowing through the terminals ( X2-1, X2-2 and so on are terminals).
In UG163 page 1, the introduction of sunlight immune proximity module maybe error, it should change Si1153-AA09 to Si1153-AA9x.
To answer my own question.
The CRC-8 is NOT Maxim even though it has a polynomial of 0x31.
Maxim has both input and result reflected whereas the si7006 CRC does not.
What am I misunderstanding?
When I send the si7006 a measure temperature command 0xF3 I receive the expected 3 byte reply.
For example: 0x76 0x70 0x99
This is supposed to be MSB, LSB and CRC in that order.
0x7670 = 30320 = 34.4 Centigrade which correlates with independant temperature measures.
So far so good.
However I would like to check the data transmission by verifying the CRC
The polynomial is documented as being X8, X5, X4 + 1
However the CRC for two bytes with values 0x76 and 0x70 using a CRC-8 with a polynomial of 0x31 and a start value of 0x00 (ie CRC-8/Maxim) is 0xD2 not the 0x99 I receive.
In fact, none of the byte triplets I receive from the Si7006 have the correct CRC.
As I doubt that any of our data transmissions are actually being corrupted I assume I must be calculating the CRC incorrectly.
Perhaps you have to reverse the bit order or something.
I have tried everything I could think of but never get a correct CRC.
Can anyone help?
Other sample data is (0x76,0x08,0xD8) and (0x75,0xCC,0x76)
I have couple of questions.
1) We have a designed a system with Si7007. The device temperature readings are accurate as it was from the beginning but the humidity readings slightly drifts with time. What could have caused the drift in the humidity readings? The same sample device reads different values when its tested against same reference meter after 6 months. Its about 2 to 3% difference.
2) 6 months ago when the 1st set of devices produced by us, the device's humidity test results of all devices are found 3 to 4% lesser than a NIST certified reference TH meter. Now when the 2nd set of devices are produced , in the humidity test results of all the devices are 8 to 10 % lesser than the 'same' reference meter.
In both the time, the temperature tests are always with +/- 1%. What could have caused the change in the 2nd set of devices produced. We use the same design. We just purchased a new set of Si7007s and the PCB is newly fabricated from the same gerber files.And we strictly follow the same assembly process both the times.