The HC-SR501 circuit board has solder pads for two additional components. These are usually labeled as ‘RT’ and ‘RL’. Note that on some boards the labels may be covered by the “dome” lens on the side opposite the components.
RT– This is meant for a thermistor or temperature-sensitive resistor. Adding this allows the HC-SR501 to be used in extreme temperatures, it also increases the accuracy of the detector to some degree.
RL– This connection is for a Light Dependant Resistor (LDR) or Photoresistor. By adding this component the HC-SR501 will only operate in darkness, a common application for motion-sensitive lighting systems.
The additional components can be soldered directly to the board or extended to remote locations using wires and connectors."
Are you sure what you are saying?
I took 1-2 hours to search for answers in several languages! I did not find such an answer! Do you think I didn't do it, I'm just wasting my time, as well as others, to send me to the datasheet?
Where else do You expect to find the data You're searching for? Where do You expect helpers to find it?
I did a number of attempts to find answers. I tell You that the links found by Google points to the worst crap of "datasheets" I've ever seen. They have been like jokes. Never seen something like that before. It looks like sales sites.
You're "hot" for finding a way to boost performance of the device. Fully okey.
How much have You achieved so far? I ask You for code and schematics.
Before the Internet provided datasheets engineers were buying data books, especially for advanced circuitry. "Standard" CMOS or TTL data books had sizes like bricks. I've been reading that "literature" for some 45 years by now.
First thanks for the answer and help!
By the way ... I've seen this before. I don't see it writing RT data inside it.
And for RL I don't need it because I don't want this option to be used.
Thanks again.
Did you see somewhere that it says exactly the model of the thermistor "RT".
Which model should I look for and with what values? I can't see it described!
Had a closer look at this.
RT is connected parallel to R6, which sets the gain for OP2 (10k:1Meg ratio).
I expect that if TR is fitted, R6 is not, so I expect (educated guess) a 10k NTC there.
NTC means OP2 gain/sensitivity increases with lower temps (and decreases when hotter).
Leo..
