Cheap Motion sensors , chinese I think

[duke37]

My maths are pretty hopeless but I joined a 33K with a 2K and measured as 2.5K so it seems a bit low but I'll give it a run thanks

If two resistors are connected in parallel, the resulting resistance MUST be less than the lower one.

1/33k + 1/2k = 1/1.89k

 

[AprilSteel]

OK sorry to be so long winded . Took me some time to get some time.
Thanks KTW . Worked well . I''ll mark this as solved (Cant do it here ,no edit)
Been mentally working on this for two years so you have done me a great favour.

I just removed the 30 K R14 and replaced with a 2.2K and that on its own got the Min to about 30 secs which is a perfect starting place. Thanks indeed .

 

[AprilSteel]

If two resistors are connected in parallel, the resulting resistance MUST be less than the lower one.

1/33k + 1/2k = 1/1.89k

Yeh remembered how to do it now .
The process is 1/33+1/2=2/66+33/66=35/66=1.89. Phew!

 

[73's de Edd]

AprilSteel . . . . . . . .

Your closeup photo of your unit, precluded picking out fine foil path detail / routing.
Refer to this closeup and the app note at the side.
Since you have minumized the R factor of the R-C time constant already, just work with halving
the C value and make a test timeout . If you grossly err, hopefully using the resistance of the vari pot will let you correct enough to trim into your new shorter activation period.. If not , keep playing with slightly decreasing C value.
You probably will not have cap measuring capability or surface mount stock, so use a conventional leaded ceramic cap . . . or mini poly.

CIRCUITRY REFERENCES :

Edit . . . .I pulled up from browser memory and thought that I was adding onto page 2 end . . .but I now see that more was added earlier on . . .after I saw my post showing up much later.

73s de Edd

 

[duke37]

To calculate parallel resistors, use a reverse polish calculator - there is no need to phew!
33 1/x
2 1/x
+
1/x
gives 1.89

I cannot get my head around the new arithmetic calculators.

 

[AprilSteel]

Got no idea how that works duke.

Thats interesting too thanks Edd . How would I go about adding the LDR mentioned on pin 9 ? R2 and R3