An alternative to using a zener would be to connect a normal silicon diode in series with the 220Ω resistor. This would have the advantage of not wasting solar cell power in the zener.

Wouldn’t the diode block current from flowing back to the solar panels ground at night?

 

Not if you point it the right way, i.e anode connected to 220Ω resistor .

 

Not if you point it the right way, i.e anode connected to 220Ω resistor .

Ok, so the current will flow from the anode to the cathode and drop about .7v at the PNP base during the day and at night (0v) the diode will not block the base from ground? Would this be the right diode to get?
https://www.amazon.com/gp/product/B0173B5G8E

 

Yes. Almost any silicon diode will do.

 

Great, I look forward to trying it out, thanks.

 

Yes. Almost any silicon diode will do.

Actually no. A schottky is always better for blocking diodes, especially when dealing with small panels like the TSs, every little voltage dropped saved by the diode can be used for the battery.

But I am not sure a blocking diode is needed unless the TSs configuration changed. The controller should act as a blocker. The diode should not be needed unless the datasheet calls for it.

 

Actually no. A schottky is always better for blocking diodes, especially when dealing with small panels like the TSs, every little voltage dropped saved by the diode can be used for the battery.

Even here? The transistor base must be pulled low enough to turn on the transistor. Whether voltage is dropped across the diode or across the resistor in series with it seems irrelevant.

 

Even here? The transistor base must be pulled low enough to turn on the transistor. Whether voltage is dropped across the diode or across the resistor in series with it seems irrelevant.

As long as the panel is wired direct to the controller. I guess that would work.

 

Yes. Almost any silicon diode will do.

I,ve completed a prototype and everything is working as it should except for the silicone diode between the pnp base and 220 resistor. If I remove it, the leds work as they should, but now I am concerned with too much voltage at the base. Would a photoresistor in place of the diode make more sense?

 

If I remove it, the leds work as they should,

What happens if the diode is present? LEDs just dim, or not on at all? Did you have the diode the right way round?

 

Nothing happens when the anode is connected to the resistor and cathode to the base. If I reverse it, I get a very dim light...

 

With the diode oriented to give a dim light, try halving the resistor value.

 

It’s a little brighter but no where near full power, halved or with no resistor.

 

Then I'd revert to the zener arrangement.