Projects > Power supplies

SSR01 - substitute H1 with zener?

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tk-don:
Hi,

I'm building a 7V SSR01 using a 9V AC supply, which when rectified and accounting for losses should give nearly 12V output, which should be ok with the SSR01 with AD825 I hope.
The PCB will be partly visible through a perforated cardboard inside an old tube radio, and would like avoid any shining LEDs if possible.

Would it thus be possible just to use a 2.4V zener diode instead of H1, and just leave R3 at 2.2k? Or is the base current of the BC556B negatively affected by this (as I-V characteristics of zeners and LEDs are not the same)
Or would it be possible to even use a 3.3V zener like used as DZ1, possibly lowering the value of R3?

peranders:
I'll suggest that you take three 1N4148 in series instead or put the led in a shrink tube or paint it black. If you increase the H1 voltage, then the drop out voltage will increase and then you'll need to adjust the voltage of the IC1.

tk-don:
Great, thanks P-A. I found a rubber cap for a rocker switch which fit perfectly ontop of the LED. Otherwise the assembled SSR01 works excellently it seems - 6.97V output spot on with the calculations.

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