How does this look?
I'll think out a loud again, just to progress things.
First of all I've updated the circuit sketch to include some changes I 've included..
Secondly I need to correct my earlier calculations, I did get it wrong (by a factor of 10) so I'll show the calculations, to make it easier to spot any errors there.
I've added a potentiometer, to provide a means of adjusting the time delay, and at the same added a resistor in series with the potentiometer, to prevent a 0Ω reading, (I think the lowest is resistance 2Ω, but it will still drain the battery fast I expect)
New calculations using
Time (seconds) = 1.1 x R x C look like this...
The resistors separately
1.1 x 39KΩ x 47µF = 2.0163sec
1.1 x 39000 x 0.000047 = 2.0163sec
+
1.1 x 5MΩ x 47µF = 258.5sec
1.1 x 5000000 x 0.000047 = 258.5sec
= 258.5 + 2.0163 = 260.5163 sec
OR together
1.1 x (39KΩ + 5MΩ) x 47µF = sec
1.1 x (39000 + 5000000) x 0.000047 = sec
1.1 x 5039000 x 0.000047 = 260.5163sec
Gives the same result, delay range now being approx 2 seconds to 4 minutes 20 secs.
I've tried to fill the gaps in my knowledge with "uneducated guesses",
I'm particularly concerned about which transistor to select.. I've taken a real flyer by selecting the one I have, also
I'm not sure if the Diode I've selected is correct. I've added the diode to try and prevent a backfeed corrupting the MO (motion sensor) signal when I supply the unit from the USB. (I guess you can tell this unit was fairly cheap!!
) I'm not sure if it will work, but I'm more concerned about whether or not the addition of the diode will effect the timer output.
I have put together a parts list which may do the job without exploding, I'm not sure !!
Resistor: 2W Res 39K D39K £0.21 **broken link removed**
Potentiometer: Hor Encl Preset 5M N46BR £0.34 **broken link removed**
Capacitor: Minelect 47uF 16V VH11M £0.12 **broken link removed**
Timer: TS555/6CN Low Power Timer RA76H £0.75 **broken link removed**
Timer Socket: DIL Socket 8-Pin BL17T £0.20 **broken link removed**
Transistor: BC558/B 30Vceo,-100mA,500mW,220/475 min/max, 100Hz, QQ17T £0.26 **broken link removed**
2.5MM JACK SOCKET: 4Pole - MJ-068H £1.43 per 2
2.5MM JACK SOCKET, 4P - MJ-068H
2.5MM JACK PLUG: 4Pole, METAL - PSG02797 - PRO SIGNAL £0.77
2.5MM JACK PLUG, 4P, METAL - PSG02797 - PRO SIGNAL
Diode: 1A Schottky Barrier Rectifiers 1N5817 JA46A £0.22 **broken link removed**
PCB:
Box:
Any comments welcomed, I really am working in the dark without a few comments to go on.
Thanks in advance for looking.