jmx66
Member level 5
Hi all,
I only need a power on delay circuit, roughly one second or two,to energize a SSR.
The original board had a 2PST relay, and cut Live and Neutral , so i use also 2 SSR, in this schematic.
I found 2 circuits on the web, and had questions about .
LM555
My choices:
-Current :10 mA for the LS240D12 , sufficient to work and get a safety margin?
- Delay: R1 =10 kOhm C1 = 100 µF T= R.C ≈ 1s
- R2 : 10 kOhm 1/2 W
2N3904
I made a mistake for Ib !!!!
Ic/ Ib = 10 so for Ic = 10 mA I got Ib = 1 mA Right?
Math for Rb: Rb= ( Vs -0,7) (2.Ib) Rb= 4150 Ohm and 1/2 W
R1 and C1 as above.
As usual, could it work?
Thanks a lot and happy new year to members and your families.
Regards.
jmView attachment 2N3904.pdfView attachment datasheet-LM555.pdf
I only need a power on delay circuit, roughly one second or two,to energize a SSR.
The original board had a 2PST relay, and cut Live and Neutral , so i use also 2 SSR, in this schematic.
I found 2 circuits on the web, and had questions about .
LM555
My choices:
-Current :10 mA for the LS240D12 , sufficient to work and get a safety margin?
- Delay: R1 =10 kOhm C1 = 100 µF T= R.C ≈ 1s
- R2 : 10 kOhm 1/2 W
2N3904
I made a mistake for Ib !!!!
Ic/ Ib = 10 so for Ic = 10 mA I got Ib = 1 mA Right?
Math for Rb: Rb= ( Vs -0,7) (2.Ib) Rb= 4150 Ohm and 1/2 W
R1 and C1 as above.
As usual, could it work?
Thanks a lot and happy new year to members and your families.
Regards.
jmView attachment 2N3904.pdfView attachment datasheet-LM555.pdf