For my project I have to switch analog signals in certain combinations. I was going to use reed relays since I prefer to have the least amount of degredation of the signals from the circuit(which consists basicaly of turn on and off the signals in different combinations). I have several questions about relays though that I need to be aware.
- Do relays retain there state with no power? At first I thought that one had to switch on the relay by continuously supplying power(i.e. the "contacts" wouldn't "snap" into an on or off state and say there without power)... but I'm not sure about this since I've seen some "on" current and "off" current in the data sheets of some relays. If it is true that one can just pulse the contacts with the appropriate current to turn them off and turn them on this would mean that they would require no power when not being switched?(which is what I would like for my project since it minimizes the power used since I don't switch very often(few times a min at most)).
- How do analog switches that use semiconductors compare to relays? I can get 4x's the number of switches at about the same price as one relay(and I will be using about 30 relays). Obviously the analog switches have to be continuously powered which is a drawback but the main thing I'm worried about is how they will affect the signal. Unfortunately I can't seem to find any data on that aspect for the relays or analog switches.
- I will be using some simple microcontroller to control the relays but I figure that they probably can't supply enough current to the realys to switch them... I guess I have to read the data sheets and figure out if they can or not and if they can't I will have to use a transistor to control the relays?
- Whats the difference between voltage and currents sensing relays? I thought all relays needed current to switch? Hence is it just a matter of how much(i.e., "current sensing" requires a much larger current and voltage sensing requires a little?)?
- The only relays I can find seem to come 1 per IC. Is it possible to find ones that are like spdt(but they alternate so one switches off when the other switches on)? or even more like how one can get quad analog switches but instead get quad reed relays(or whatever).
and the last question
- Where is a good site to buy components from? Right now I've been looking at Jameco and Newark but Jameco is pretty expensive and as few products but is easy to navigate and search yet Newark is cheaper and has tons of stuff but can be very confusing at times on what they are selling and where its located.
Thanks for any help, AD