Author Topic: SSR01 - substitute H1 with zener?  (Read 271 times)

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Offline tk-don

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SSR01 - substitute H1 with zener?
« on: March 10, 2019, 09:38:51 PM »
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?
« Last Edit: March 11, 2019, 11:04:34 PM by tk-don »

Offline peranders

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Re: SSR01 - substitute H1 with zener?
« Reply #1 on: March 21, 2019, 07:23:19 PM »
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.
« Last Edit: March 25, 2019, 06:59:12 AM by peranders »
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Offline tk-don

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Re: SSR01 - substitute H1 with zener?
« Reply #2 on: March 24, 2019, 09:55:15 PM »
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.