Remote Control Devices (for WFP Trolley Systems)I have built my own trolley system to use for Water-fed poling. As any trolley user will know, the system uses a lot of water, and a major problem with a non-van mounted system is the need to refill the the tank frequently.
As with some systems, I have just fitted a remote control device to the system to allow the pump to be switched off by means of a keyring-type transimtter like this:
Now, there is a great pitfall with these remote controls, that cost me some money. There are 2 basic types, those that use the AM radio band and those using the FM band (usually around 433 MHz)
AM Band - A Fundamental FlawI first bought an AM band transmitter and receiver pair, they came in kit form, so some building was required. When I had tuned the transmitter to the receiver the system worked fine. The range was about 25-30 meters which is more than adequate. BUT, there was a serious problem when attaching it to the trolley. The pump could be remotely switched on, but NOT switched off again. I checked the tranmitter, fine. Checked the receiver, fine too. They worked fine together, when not connected to the pump. But no go when connected. I vaguely remembered someone else having the problem that the remote would switch the pump on but not off again, and here is the reason why.
The water pump (as do all diaphragm pumps) contains a
unsuppressed motor. What this means is that when the pump is running, it emits some radio interference. And yes you guessed it, the interference is in the AM band. (Hence if you put a normal radio near to a running pump, you hear crackling)
This interference affects 2m in all directions of the pump, and was more than enough to completely block the transmitter signal. The result was that the pump could be remotely switched on, but NOT off again. No good.
FM Band - OKSo, I bought a new tranmitter and receiver pair, this time an FM system. Installed it and it works perfectly. The range is approximately 35m .The nature of FM radio signals means it is less affected by interference of any kind (thats why you can have FM stereo but you dont get AM stereo). The pump motor does not affect this at all.
So, save yourself a lot of hassle if you're looking into this type of thing.
Get FM not AM.
-Philip
Now have a look at this
http://www.cleanitup.co.uk/cgi-bin/yabb/YaBB.pl?board=usedequipment;action=display;num=1082756232;start=0#0
