# PIR hc sr501 sensitivity

#### gwidijanto

Jun 28, 2023
3
to increase sensitivity in hc sr501,
which direction of 1Mohm trimpot must turn?
toward minimum i.e = O ohm or
toward maximum i.e = 1M ohm?
tq

#### Delta Prime

Jul 29, 2020
1,223
Depends on the configuration of your trim pot! And how you hooked it up!
I would start in the middle 500K ohms.
But since I've used one the exact same one my findings are.
Full CW, the range of sensing increases, and the maximum sensing distance range is approximately 0-9 meters.
Full CCW, the distance is reduced, and the minimum sensing distance range is approximately 0-5 meters.
CW=turn it clockwise!
CCW=turn it counterclockwise!
You got a clock? Do you have a lens on your detector?
What's the matter cat got your tongue?

[mod edit: removed unlicensend stock image]

Last edited by a moderator:

#### Bluejets

Oct 5, 2014
6,583
According to this and the spec sheet (DOH!!!!!)

................ CW to increase.

Moderator
Nov 17, 2011
13,337

#### gwidijanto

Jun 28, 2023
3
Depends on the configuration of your trim pot! And how you hooked it up!
I would start in the middle 500K ohms.
But since I've used one the exact same one my findings are.
Full CW, the range of sensing increases, and the maximum sensing distance range is approximately 0-9 meters.
Full CCW, the distance is reduced, and the minimum sensing distance range is approximately 0-5 meters.
CW=turn it clockwise!
CCW=turn it counterclockwise!
You got a clock? Do you have a lens on your detector?
What's the matter cat got your tongue?

[mod edit: removed unlicensend stock image]
tq for your answer, why I ask it, because if you search this topic, some said CCW increase sensitivity, other said decrease.. confusing.. so to make sure I ask using resistance of the trimpot:
to increase sensitivity,
which direction of 1M ohm trimpot must turn?
toward minimum i.e = O ohm or
toward maximum i.e = 1M ohm?
tq

#### Delta Prime

Jul 29, 2020
1,223
toward maximum i.e = 1M ohm?
Yes towards maximum sorry buddy thank you for the thorough explanation.

#### Delta Prime

Jul 29, 2020
1,223
As usual: RTFM
I don't speak moderator
I know I just made... double secret probation

#### gwidijanto

Jun 28, 2023
3
tq Delta Prime,
this is confusing me

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#### Delta Prime

Jul 29, 2020
1,223
Okay I'm wrong,I think, I don't know anymore!!
Turn it all the way to the left counterclockwise stand 7 meters away and jump around ...see what happens. As everyone else can tell... it's past my bed time.
Good night!

#### Delta Prime

Jul 29, 2020
1,223
Or what is confusing you the two potentiometers? Just turn the one on the right with the arrow forget about the other one. And jump around 7 m away

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,337
I don't speak moderator
This is no moderator speak, this is common internet slang: RTFM.

#### Delta Prime

Jul 29, 2020
1,223
Ooh ooh. Touche. Thank you sir. Good night.

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,337
which direction of 1M ohm trimpot must turn?
toward minimum i.e = O ohm or
toward maximum i.e = 1M ohm?
The resistance of the trimpot is constant (measured between the endpoints). What changes is the divider ratio which varies with the position of the wiper. Typically one would connect the wiper and the endpoints in such a way that the divider ratio is maximum (i.e. approx. 0) with the wiper in the leftmost position and minimum (i.e. approx. 1) with the wiper in the rightmost position. But this is by convention only. One can also swap the endpoint connections and the behavior is reversed.
Also the divider ratio alone doesn't tell you which is more sensitive or less sensitive. This depends on how the potentiometer is used within the circuit.

Another source of confusion: sometimes cheap cloned boards from PRC are constructed not 100 % identical to the original board and may behave differently than the original.

Therefore: RTFM.

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