View Full Version : Top-off float switch concerns

03/06/2002, 12:41 PM

I read your article in the march issue of Reefkeeping.

I have a few concers about the water top-off design you are proposing:

- it puts high voltage in the tank :eek2:
- with high current the Reed switch inside the float switch will stick on the closed position because of electrical arc soldering :eek:

The circuit is really in two parts:

- provide electricity to the pump
- provide electricity to the switch

If you include a small 12V tansformer between the main and the rectifier, you aleminate the high voltage in the high current in the Reed switch.


This modification add a few bucks only to the whole scheme, but is much more safer and reliable.

Additionally, you can use as well low voltage everywhere and use as 12V winshield wipers pump or a RV kitchen sink pump (food grade).

My web page (http://www.camel-reef.com)
[URL=http://camelreef.geekopolis.com]My web page's overflow

03/06/2002, 05:36 PM
You missed the full wave bridge rectifier and 2K ohm voltage dropping resistor in the schematic. The float switch has a low DC voltage on it not AC.

03/20/2002, 09:02 AM
Do you happen to have the Hosfelt parts number for the relay? I'm getting a little confused trying to find the right one. Thanks

Keith Hurley

03/20/2002, 08:40 PM
I built one of these a few years back, my experience was that over time the switch would latch. Was this due to age or some other malfunction, i do not know. However, I re-designed the system and used the float only to drive a transistor which in turn sourced the current necessary to drive the relay, only a few mA flow through the float now and I have had no failures of the system since the mod. An alternative would be to use the float to trip an Opto-coupler with a TRIAC out and a Triac to switch the AC line, that may be how I will set my next system up. One slight difference with mine is that I wired up a 555 timer as a single shot with a trim adjusted gate. This allowed me to eliminate the jitter associated with the turbulence on the water surface and needless power cycling to the pump, this may not be necessary but, i felt better putting it in as a saftey none the less. I have had mine running now for about 3-4 years.

My arrangement is certainly more expensive than that which was discussed here, but i built in indicator lights to let me know if it was functioning properly at a casual glance and some other things for my peace of mind...

Just my thoughts...