question about relay build (ger21 maybe) about the resistor

[timmyb199]

hi again thanks for all the past help here is my questions

if i get a solid state relay with 5 volt input 120vac on other side can i hook it directly to a pin for mach three with input high and it will work to turn on motor? the other side to ground of course

what is the need for the 300 ohm resitor from board to relay in all the digrams i see?

i have limit switches hooked up on a xylotex board (the new 3 axis) through mach three they work fine, but i have read to put a resistor betwwen swith and board, am i gonna blow something up ? the xylotex manuals online dont seem to say anything about the resistor, is this just for the older xylotex boards?? the posts seem to be from 2005

thanks again

timmyb

[timmyb199]

anyone?? i will read site more , answer must be abvious

[Al_The_Man]

I am not familiar with xylotex board but may be able to shed a little light on SSR in general.
I assume they may have been referring to using a solid state isolator IC with no limit resistor, and in that case you would use a 330 ohm resistor when used on 5vdc.
If you use a SSR module, they are already current limited and you buy them for a particular input voltage, i.e. 5vdc, 10~24vdc etc, in these cases they do not require a resistor, but they can take up to around 20ma to switch, which means that the circuit you are using to switch the SSR has to have the capability to switch this current.
If the board you are using uses a 6 pin IC with something like 4n25 etc, then you probablly need a resistor on the input.
If you place a link to the board you are using I could check further.
Al.

[timmyb199]

here is a link to the board i have

www.xylotex.com/3axBoard.htm

[Al_The_Man]

It appears the Xylotex board passes the parallel port pins through, unbuffered, which means that the paralell port will have to be able to drive the SSR, I would imagine many used a breakout board of some kind to buffer for SSR's, you could also use a cheap single buffer such as the 2N7000 transistor, if you do a search here there are several examples. http://cnczone.com/forums/showthread...92&page=6&pp=5
Al.