this is a design for a water level probe that i have now on my work bench and try to get some improved working
it was pretty sensitive (relais chattering) before i put the capasitors in but i am afraid that if i make the probe cables longer they still pick up noise and don't work properly
the resistance of the water between the propes is measured over the farest probe litle under the 2 M ohm would that be suficient if i would put a normal capacitor on 10 n between the probe and comon probe???
the resistance of the water between the propes is measured over the farest probe litle under the 2 M ohm would that be suficient if i would put a normal capacitor on 10 n between the probe and comon probe???
Thanks for all the sugestions
as shown in the shematic this is as i have build it now and it seems to work fine on my work bench
put the extra inverters in to the circuit to get a better efficiency as the purpose is that the Water tank should be full so that means the relais are now in the new schematic only activated when the level drops
for a sump it would be other way around
still another question
about the hum in the suply (as eric mentioned)
the suply comes from the 7812 and accompanied with the usual capacitors
is it still advisable to use shielded cable??
its my intention to put the the whole circuitry as close to the probes as posible (3 meters Max) and that only the relais switch contacs will be wired to the main control panel so that is already a different circuit
that's nice for indication but i have to switch the control contactors that switch the pumps so relais would be the best/economical solution
the relais are the small print relais and they are located in a pump room so there is no way you will notice the sound of the relay withe all the sounds that the pumps are making
Eric thanks again for your advise, consider it done
the decoupling capacitor (100nF) i always put next to any Cmos IC but often forget to draw it in a schematic during the "designing phase" and put it in the drawing when everything is finished
instead of the leds use 5v relays or triac opticouplers might be better.
the use of the opticouplers would isolate the 110 from the rest of the circuit in a safe manner..
MOC2023 come to mind.
instead of the leds use 5v relays or triac opticouplers might be better.
the use of the opticouplers would isolate the 110 from the rest of the circuit in a safe manner..
MOC2023 come to mind.
at first i design all pump swich panels with 24V control voltage
i do this because the panels are in a wet envoirement and maintainance personel here in cambodia is not that high qualified in schooling (if the have any) so that small acidents happen more frequently here than on other places in the world
The second thing here is that getting the part here that you want result in long waiting times and inconsistend delivery if availible in asia
so i am more or less depending on what is localy available and believe me that is not that much
Still i have to control the cost also against the reliability and posible problems and a relais is still a good, reliable, easy to exchange, cheap and easy to get device