how to interface 8051 and a contactor/relay?

geyser control with 8051

hello everyone..i am doing a project on water heater control using 8051. Can anyone tell me how to interface 8051 and geyser(water heater) through a contactor/relay?? My doubt here is 8051 is low voltage output and geyser is a high current device. So how should it be done??

Re: geyser control with 8051

A Mains-Powered Load can be controlled by a microcontroller in two different ways:
- microcontroller -> optocoupler -> triac
or
- microcontroller –> transistor -> relay/contactor
or combination of the above ..

See examples at:
**broken link removed**
http://www.mikroe.com/en/books/picbook/7_05chapter.htm

Rgds,
IanP

Re: geyser control with 8051

Hi,

you can connect this device through high current relays with fuse. Required current depend on the load (the devices that you need to connect)

As IanP mentioned you can interface this device to your controller. And also I like to add few things to that

microcontroller –> opto-isolator-> relay -> Fuse -> Load

or even better if you need high power load then

microcontroller –> opto-isolator-> low amp relay -> high amp load relay -> Fuse -> Load

however this depend on your actual requirements

also you may look this post also

EDAboard.com Forum Index -> Electronic Elementary Questions > Variable speed control on a 12v DC motor that draws 40 amps

Click to expand...

regards
bassa

Re: geyser control with 8051

thank you both!! as bassa improved the circuit i shall first find out what our apparatus needs and understand whatevr components u have suggested of and then make a query with you thank you

Added after 11 minutes:

AND just one more doubt before i start off.. I am not understanding the concept that how much voltage ouytput is an atmel 8051 delivering out? and on what grounds should i understand the coupling of all the devices because the geyser is a current controlled device and 8051 supplies voltage puilses as low as 15ma:| so could you please explain that to me li what is the concept behind this part of coupling??

Added after 4 hours:

and ya mr.Ian.P i read from archives which is on this linh which i think you posted in 2004 :!: .. got a clear cut info of the components and i read about the triac triggering also.. so now the clarification i need is whether i could connect 8051 to MOC3021 and then triac BT137 or SC141D and then hook it to the geyser?? i matched the trigger current levels and so on and found matching but waitin for your confirmation ofcouse fuse also i shall include as u said.

Added after 1 minutes: