solid state relay to control lathe motor...anithing alse?

[patriciooholegu]

hello people.
Last weekend, working on one of my many many projects (a home made cnc lathe) i found a solid state relay on a photocopier machine, rated to 240 volts and 16 amps max. The control side as labeled 4-8 volts.
very happy with this (I didnt notice this fellow before), tested by conecting to a induction ac motor and directly to the parallel port on my computer on the other side: It worked on the first attempt!!!
Now, im wondering: I need anithing alse?
Maybe a 1kohm resistor from the parallel port pin, or a small capacitor for-wathever-reazon-of-electronics there is?.
wath do you suggest to ad to improve this?
The objective is to control RPM trough Mach 3, using the sistem they suggest (I didnt describe it because, maybe you notice, my language it is not English and this is already very painfull to write for my).
So, waiting for suggestions.
chears.

[Al_The_Man]

I prefer to buffer the P.P. using for e.g. a 2N7000 transistor, the output or drain of this FET would go to the SSR and no resistor needed, the PC 5v could still be used.
This system will not be able to control the RPM, due to the SSR being a switch (on/off).
And a 1 ph induction motor is unsuitable to be used with speed control.
Al.

[vger]

Those photocopier SSR's are good. Many of them have 2 SSR's in the same package. One part controls the main photocopier motor, and the other controls the heater in the fuser section. They are generally opto-isolator input.

Do you have a speed control already on your lathe?

Steve

[vanjast]

What worries me is that the SSR requires 4-8 Volt control input levels

A parallel port (the last time I looked) has TTL input/output levels 0-5Volts, but in reality you're looking at ~4.6V@0mA (no load), to 3.2V@~10mA (max load).

What you need to do is get a datasheet on the SSR (google) and check the input current requirements of the 4-8V signal. This is usually an optocoupler where 5mA should be the drive current. This will put you,possibly, on the limit of the parallel port/SSR drive capabilities, causing unreliable SSR operation.

[Al_The_Man]

This is why I prefer the buffer, the 5v for the SSR can then come directly off the PC P.S. via one of the 4 pin supply sockets.
This has worked well so far.
Al.

[LeeWay]

I run an SSR for my coolant relay on my mill and use the same on my router without anything else. Just straight wired. The Breakout boards I use have 5 volts available that doesn't come from the PP. I use that and have never had a failure to energize or shut down.

[patriciooholegu]

Tank you all for your answers.
I googled the dam thing (That was the first thing i did) and IT NOT EXIST ON THE WEB.
The relay is KOMEKO DZF-16A
With that of 4-8 volts they suggest that you are able to controll the thin with voltage betwen 4 to 8 volts.
So sath it didnt work for rpm controll on mach 3.
but i have undestand that PWM it is already some kind of fast on/of condiction (if you use, for example, a triac)and this should be the same?

Wathever, the ssr as being added to mi "cnc lathe" shue Box... (A box for shues, were im putting all the things which will be my lathe in the future. So far there is 2 vexta 5 phase motors, the controller boards, 2 PC power supply in series -to have 24 volts at 18 amps- and other staff im not able to remember).
Do i need optocoupler betwen Parallel port and SSR? or it is a SSr some kind of isolation?

Chears.

[patriciooholegu]

Al_The_Man do you suggest using the called "Dimmer" (TRiac) to make PWM on a AC motor from Mach3?
I was in the knowledge that SSR was to make the same job than Triacs, but better...
May be im wrong.

[Al_The_Man]

Originally Posted by patriciooholegu Al_The_Man do you suggest using the called "Dimmer" (TRiac) to make PWM on a AC motor from Mach3?

What post are you referring to?

Originally Posted by patriciooholegu I was in the knowledge that SSR was to make the same job than Triacs, but better... May be im wrong.

In the case of the SSR with triac output, you do not have the ability to vary the phase angle that it switches at due to its built in feature of being a switch.
IOW it is either on or off, this is what it was designed to do within a SSR, so you cannot vary the degree of conduction to enable it to be used as a variable speed controller.
You either need a unit designed as such or put one together from descrete parts.
Al.

[Andre' B]

Originally Posted by Al_The_Man And a 1 ph induction motor is unsuitable to be used with speed control. Al.

Speed controls are availably for 1 ph motors but they are more expensive and not really intended for things like spindles. Seem to be more for fan and pump type applications.
Invertek Drives AC Drives, Drives, Inverters, and Control Systems

[Al_The_Man]

I know the ones I had experience with could not be used with Capacitor start only motors, they could only be used with Cap start/run, these may have slightly more features.
This link today was interesting for a design based on turning a split phase motor into a 2 phase motor.
http://www.cnczone.com/forums/pic_pr...rograming.html
Al.