[Solved] Input wanted on wiFi controlled water valve

@will Ok, but why? I got those values from a circuit design on-line. They seemed to know what they are doing, I sure don't but generally understand what ripple is. Are you recommending 10 vs 1 because 10 will take out more ripple? I have no problems with overkill even for something as utilitarian as this.

@zander 

I just use 10 uF as a habit I got into long ago. It came from some YouTube channel I watched years ago. Your use of 1uF is certainly enough for the small current you'll be using.

You'll note that I said "I'd go" instead of "I'd recommend".

Your choice is perfectly acceptable and probably more correct than my habitual selection 🙂

IF the diode is needed and I am beginning to think it is at least 'best practice' then what kind. I did google it but only encountered new terms I don't understand well enough. It looks like a Schottky diode is what I want. Only needs to block 5V and pass a ? amps. Is the inout to a SSR measured in ma or amps?

@zander 

I just use 10 uF as a habit I got into long ago. It came from some YouTube channel I watched years ago. Your use of 1uF is certainly enough for the small current you'll be using.

I got curious and went back to check the original video in a channel run by afrotechmods, here's the URL for the video, it's quite informative (although old) ...

He uses a 10uF electrolytic and a 0.1uF ceramic on the output side, so we're both in the zone 🙂

@zander 

The SSR's I'm familiar with (i.e. the cheap ones) are usually in the single digit mA region.

Not sure what diodes you're referring to ?

@will I need to add an emergency bypass switch to the cloud part so that if some part of the cloud fails and drops the relay I can pick it manually. Since it's 5V, all I need is a switch between the 5V input line and the esp8266 output pin. I am unsure if it's a good idea to just put 5v on a pin even though it will output 5v so want to add a diode. Learning as I go here that sounds like a Schottky diode? My question then becomes which one, anything greater than 5V sounds good and able to pass less than an amp but more than ???20ma???.

@will I see he is using a 10mf in parallel with a 0.1mf on the output. According to my ancient knowledge that just means it is effectively a 10.1mf cap. Why bother with the extra 0.1? If the rule was a cross product, then 10 x 0.1 is indeed 1. Puzzled is me.

@zander 

I presume that the diode is intended to prevent current flowing backwards into the ESP.

The Schottky diode offers a much lower voltage drop across it than a "normal" diode. Depending on how much voltage you need to trigger, you may even be able to get away with a regular diode.

You can choose any suitable diode by making sure that it can (easily) handle the voltage and current expected.

@zander 

Different constructions, electrolytic vs ceramic. I believe that the ceramic can handle faster draws but smaller amounts. So having the pair provides good short and longer term supply capability. I think that's required for things that will occasionally have a very large draw for a very short time.The electrolytic has mostly a shooting function.

I'm out for a while now ...

@Zander, @Will, Ceramic capacitors have much more tolerance to high ripple than electrolytic's, but because of the size  low ripple in linear voltage regulators, they tend to use then more often.. In my opinion, electrolyics are can cause a lot of problems with physical leakage, and electrical leakage, and so don't recommend them used in circuits where small capacitance is required. We use to call them filter caps in the old days, as they filtered out the ac ripple in a bridge rectifier.

Regards,

LouisR

Posted by: @inst-tech

@Zander Ceramic capacitors have much more tolerance to high ripple than electrolytic's, but because of the size  low ripple in linear voltage regulators, they tend to use then more often.. In my opinion, electrolyics are can cause a lot of problems with physical leakage, and electrical leakage, and so don't recommend them used in circuits where small capacitance is required. We use to call them filter caps in the old days, as they filtered out the ac ripple in a bridge rectifier.

Interesting, then would you say that the regulator would be better with no electrolytic on the output side, just the ceramic ? If so, what would be an appropriate value ?

Thanks.

@will, A ,1uf to 1uf on a the output of the regulator would be good I think, as their is very little ripple in the output of a linear regulator.. most switching power supply that handle large current capacity are why electrolyics tend to be used as they can act as a battery and store large amounts of current helping to keep the output voltage stable. In small power applications this is not so much of a problem.

Regards,

LouisR

@inst-tech

Thanks for the explanation and insight !

@zander

Your original plan appears to be exactly what's required.

@will So 10 and 1 it is. Now the hard part at least for me, figuring out how to package it up and make the few connections needed.

@inst-tech Excellent explainer.