float swicth(reed switch)

[kimseunghee]

The normal closed contact(low level) of float switch is connected to relay in the starter but relay does still energized when level reaches low. The relay is driven by AC220V. I swapped relay and circuit with DC24V instead of AC220V, then the realy is working(drops).
The contact is laid with other signals in the same mulitcore cable at length of 300 meter.
How could I check in order to resolve ? I would like to maintain AC220V circuit. Attached please find sketch for the above.

 

[itsmoked]

Its the 300m. That's 600m round trip. The capacitive aspects of the AC power is causing your problem. You should use the DC solution.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[OperaHouse]

Is this a solid state relay? Capacitive effects of the wire could be resolved but this would be hard on the switch contacts. Notice switch is only rated at 110AC. Try a .1uF capacitor in series with 220 ohm across relay if you insist on using high voltage AC.

 

[btrueblood]

...and if you use the DC approach, put a snubber (reverse-biased diode or diode and zener in series) across the relay to keep the flyback from zapping the reed switch contacts.

 

[kimseunghee]

The relay is not of solid state relay. If relay is changed to DC relay then I also should be careful of voltage drop over the long cable. That's why I prefer to AC circuit.

 

[itsmoked]

We just went over this here: thread240-208641

Not much of a problem really.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

24V DC with a solid state relay works well over long distances. The SSR has a low burden so there is little volt-drop. A compromise between burden and noise immunity usually requires an additional resistor of, say 1k[Ω] at the SSR end, but the wide tolerance of most SSR inputs means that it will remain reliable even with volt-drops which would adversely affect a conventional relay.


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