Please I need some help

[malinmc]

I am trying to build a plant moisture meter and the curcuit can be found at this link.

https://www.free-electronic-circuits.com/circuits/plant-moisture-meter.html

I have a few questions regarding this curcuit

1) It says "adjust R5 for a mid-scale meter deflection". Where is the resistor R5 located?

2) What is the M1 that connects to earth stand for?

Any help given will be much appreciated.

I also want to know how to integrate an electronic PH meter to this curcuit? Could any forum members please offer me some help?

Could you email if possible all suggestions to mal_chand@yahoo.com

Once again any help given will be much appreciated.

 

[JimB]

R5 is the 100k resistor with the arrow thingy half way along it.

M1 is a moving coil meter.

Do you have any electronic construction experience?
All suggestions will be via the board not via e-mail.

JimB

 

[malinmc]

Thanks very much for the reply and the help advice. Where would I be able to buy the moving coil meter? If I go to an electronic shop and ask for a moving coil meter would they give me one?

 

[chemelec]

Thanks very much for the reply and the help advice. Where would I be able to buy the moving coil meter? If I go to an electronic shop and ask for a moving coil meter would they give me one?

Yes, But a 0 to 1 ma Meter will Not be very Cheap.

 

[HiTech]

Don't laugh but HF sells both a PH meter and a soil moisture meter for $5 each! And believe it or not they work fairly well... not like a professional, complex meter, but for relative indications they work good. No electronics inside, just bi-metal that generates a small current to deflect a calibrated meter. These are very rudimentary devices but if all you need is a relative indication they work fine.

Harborfreight PH Meter

Wood Moisture Meter



**broken link removed**

 

[Russlk]

Radio Shack used to sell a cheap multimeter with moving coil meter, but they are probably all digital now. You can use a digital meter with a current scale instead of the moving coil meter.