Hi,

and if you ever fire both sets of relays at the same time lots of smoke will be let out.

That is correct, if you do not correctly program and time the activation of the SSRs you risk having all four on at one time
and disaster will strike.

If however you have an input relay and a DPDT relay on the output (for motor reversal only) then you need to sequence
the input relay BEFORE switching the reversal relay or risk blowing the contacts off the reversal relay, ie you have
to correctly program and time the activations of the relays.

Correct programming is required in both cases.......either solution works and either fail if you don't time activation correctly.

Craig

The current rating of those SSRs is only 1 amp. Max surge current is 5 Amps. If one fails it can take out the others.
This is why I suggest using a cheap and easily replaced DPDT relay.

Thanks could go either way still testing..

I assume a G4 would work in the g code?..

Gary

The best way to providing reversing is to use a drive with that feature. Sometimes going the cheap route costs you more in the long run.

Also, There should be a fuse to limit the damage if when a fault occurs.

Hi,

I assume a G4 would work in the g code?..

Yes, g4 in Gcode would cause a delay whereon you can change direction......but if you omit the g4 from your
code you blow up your relays and/or your drive. You should have a script in Mach4 that runs every m3/m4/m5
operation so that an inadvertent missing g4 doesn't wreck things.

That would apply to either SSR OR relay solution.

Craig

The responsibility of providing the right timing could be shifted to the operator by having the code put up a message asking the operator to set a manual switch.

How often will a G code program ask for a spindle reverse mid-operation?

How often will a G code program ask for a spindle reverse mid-operation?

That is a very interesting question.

I think we all know that if something is allowed to happen then sooner or later it will happen. 

Tweakie.

So doesn't seem to work correctly, I wired it up per the diagram for the SSR relays

if I don't have the motor connected to both forward and reverse relays it works fine connect one set of relays and runs forward. remove forward relay wires connect the other two relays and it runs reverse.. great, but if I connect the motor to all 4 relays and turn on reverse the motor moves really slow and the plus wire from the relays turned on and the neg wire from the relays turned off over heat and smoke..

I don't see any thing wrong with the wiring so confused here..

Could I have a bad SSR relay, how to test it ?.. I did check the ohms on the outputs of all the relays 3 showed 0 ohms but one showed 278.89 ohms when relays where not power on so should be Open circuit ..

Did all testing off the mill on and old 12v motor,,


Thanks gary

Expanding on my previous question, other than tapping I don't see a case where the G code would need to control the reversing of the spindle.
What do you plan to do that would require it?
The motor is stopped when a tool is changed so a manual switch could be used.

Hi,

Could I have a bad SSR relay, how to test it ?.. I did check the ohms on the outputs of all the relays 3 showed 0 ohms but one showed 278.89 ohms when relays where not power on so should be Open circuit ..

Can you post an exact model code of the SSRs you are using? I noted that in the diagram you posted you showed the
internal representation of the SSR as a MOSFET with an anti-parallel freewheeling diode. If that is indeed the internal
structure of the SSR then you can under no circumstance reverse bias it because the freewheel diode 'shorts' the
applied reverse voltage.

As MN300 has pointed out a mechanical DPDT relay even with the addition of a SPST relay to isolate or turn off the spindle
is an easier proposition if you are not familiar with electronics. Unlike MN300 I think a suitable DPDT relay is not going to be cheap.
I have had many occasion to reverse DC motors as a result of working with welding equipment for some years.
We stocked open frame relays such as this for the purpose. They are not cheap but they are good and therefore did not come
back as a warranty claim on our work.

https://nz.element14.com/potter-brumfield-te-connectivity/prd-11dh0-24/relay-dpdt-125vdc-20a/dp/1386559

Note the price in this link is in NZD.

Craig