Hello,

I am trying to build a moisture sensor that will be in a seal environment to turn on a 24V water pump. I have found a schematic online for a moisture sense except its source is 220V, How can I adjust the component values to allow me to use a 24V source instead of 220V?

Thanks

 

Hello,

Without any schematics we can not give you an advice.
Please post the schematics.

Bertus

 

Just a pointer on this also. There's a huge difference between 24VDC and 24VAC; the latter has inrush currents in the coils of relays and solenoids - several amps often.
If it's more than taking out the power supply, I'd try for a different circuit or design from scratch.

 

220 volts AC to 24 volts DC: http://www.digikey.com/product-sear...ee=0&rohs=0&quantity=&ptm=0&fid=0&pageSize=25

 

Sorry , I thought I had linked the schematic I am attempting to manipulate.

Here is it here

I have updated it as show in the picture below to add another LM358. When the humiditiy is to low as sensed by A2, set by P1 it will activate a motor to pump water to a sponge and have a fan blow moisture through the air.

A3 senses if the moisture content is too high it needs to remove moisture from the air. I haven't quite determined how to remove the moisture, and am taking any suggestions on a good way to remove the moisture

 

I think I am going to use a 120 to 24 volt converter, as shetii01 showed the 220 to 24 volt DC above, for the components correcting the moisture level. I'm using 120 because I am in north america and I am pretty sure the schematic was completed for somewhere in Europe. If I change the source voltage to 120 rather then the 220 in the previously designed schematic how do I determine the new resistor and capacitor values?

Thanks

 

Was the power shown in the schematic directly from 220vac?
It hardly seems necessary, a circuit designed around 24vdc should be preferable and dropped by a suitable transformer supply.
This way there is no component changes necessary?
I see now you managed include the schematic link, I am guessing that will work for you on 120v.
There is a slight difference in timing, 50hz/60hz but these circuits are very tolerant for what you need it for.
Max.

 

To me it looks as though it was never dropped down because the circuit here is turning on 2 lights, which i assume are 220V lights.

 

I am pretty sure to simulate the heating effect they came up with two 240v lamps, you could use 2 120v lamps.
I doubt they used 440v versions!
R15 you may have to tailor, but try it first.
Max.

 

Perfect thanks for your help