sigmacom

DTMF, huh? Good and cheap solution, but too "classic analog" don't you think? I prefer digital; it's more secure... Anyway, I think it's perfect for our friend with the level of knowledge he has. Tips for james120479: - You can ommit the flip-flops (4013) if you don't want to hold the last state (which transmitter was last used). - Forget the 418 MHz receivers we discussed earlier. You must use a simple FM radio receiver instead.

If you can work with these chips (I say that because of your level of knowledge), then choose an RF transmitter & receiver from http://www.rfsolutions.co.uk/products/rf_modules/Am_fm.htm or http://www.abacom-tech.com/receivers.htm and http://www.abacom-tech.com/transmitters.htm Some of them are really cheap for you I suppose... Any questions? :)

I agree with this: "Solid State in my mind means not mechanical" but the schematic, can't be called "a solid state relay": As you know, relays offer isolation between the relay contacts and the coil. Also, you can control (on-off) any kind of voltages/currents, with indepedent voltage on coil. A solid state relay (the component, not substitutes) does all this, because it has a diode as coil, and photosensitive thyristors/triacs as relay contacts (for example, with 5VDC as control voltage, you can do 220VAC on-off control). None of the above conditions met by the schematic posted above, so I couldn't call it "a solid state relay". Anyway, it does it's job! ;)

Hello! First of all, I don't know these chips you are reffering to, so please give some info (URL of datasheets, etc). There are many ways to do what you want, easy, cheap, etc. Are these chips available, and if yes, what is the total money cost?

Yes, but this is not a solid state relay, as the title of this thread says... ??? ???

Is it mandatory to use 74ls283 and 74ls194?

A very simple approach, is shown in the following schematic. The 2 resistors of 1 kOhm each, make a voltage divider /2, providing a Vcc/2 voltage to the (+) pin of the comparator. This is used to set the (+) input at higher voltage vs the (-) input -and so- force the output (Y) to high state (Vcc). When voltage at pin (-) of comparator goes more than Vcc/2, then the output of the comparator (Y) goes at low state (GND) and vice versa. If you ommit the resistors, the input voltage at pin (-) must be > Vcc to trigger the output. Try it! :D

Also notice that most common solid state relays, are made to handle ONLY RESISTIVE LOADS, not inductive (like as a motor). Else they burn... There are specific type of solid state relays to handle that kind of loads. Seek for them. :)