Help with a Float Switch circuit.

Discussion in 'General Electronics Discussion' started by zgetman, Jul 27, 2015.

1. zgetman

6
0
Jul 27, 2015
I am new to the would of relays, and circuit boards. I have a little background in electrical knowledge, and am attempting a project. I am working on building an Auto Top Off for my aquarium. I have a schematic that I drew up which is found at 3reef.com. What I am needing to know is will this circuit work? Also I need to know what how many VDC my relays need to be. Will two 5v DC relays work or do I need 9v DC relays. I get mixed up with the voltage information. Any help would be appreciated.

Zman

2. Minder

3,215
700
Apr 24, 2015
Looks like you need 12vdc relays, the convention is to use 0 & 12v not +12 & -12 as this implies a dual supply.
Also you show one relay coil open circuit?
M.

3. zgetman

6
0
Jul 27, 2015
Yes, The idea is that that Open circuit will sound an alarm and flash if my water level gets to low. The first 2 switches are where pumps will be. The second float switch is what will let me know the pump that is part of the circuit is to low on water. Makes sense?

4. Minder

3,215
700
Apr 24, 2015
One side of the coil of the relay is OC, it will never operate as shown, where is it fed from?
M.

5. zgetman

6
0
Jul 27, 2015
thanks for catching that, it is supposed to connect to the -12vdc side to complete the circuit. I think that is how I figured it.

6. Minder

3,215
700
Apr 24, 2015
OK, But to analyze the circuit properly the state of the float switches have to be known in the particular part of the process, IOW what condition operates them.
M.

7. zgetman

6
0
Jul 27, 2015
The level of water in the tanks. In one tank there are two float switches the lower float switch is the first in the circuit, it tigers the alarm if the water goes below the switch. The second switch in that tank is the last in series, it turns the pump on if the water drops below it. The switch that is second in series is in the tank that the pump in the circuit is located, it sounds the alarm if the water level drops below the switch. Make sense?

8. zgetman

6
0
Jul 27, 2015
Is this schematic right? The 2 relays are 12v dc.

I have another question. With the led and alarm in circuit how do I calculate the resistor needed? Also do I place the resistor before or after the LED?

Last edited: Jul 28, 2015
9. Minder

3,215
700
Apr 24, 2015
Still not quite clear on what you have, BTW switches should be show how they are physically connected and then either by symbol or notation, mark whether they are N.C. help open, N.O. held closed etc.
IOW, they could be wired N.C. Help open when tank at normal level.
The LED and alarm should be in parallel, the resistor will be calculated depending on the LED device normal current, usually ~ 470Ω - 750Ω.
M.

10. zgetman

6
0
Jul 27, 2015

sw3 - floating switch 3
d1 - diode