[Newbie] Help me decipher wiring diagram.

[xbartx]

That's how I'd do it. But I'd probably just use a single pole relay, unless you already have the dual.

I'm hoping to use the relays on my controller, I just need to find out if they have a suppression diode on the coil.

 

[Asm109]

Its a safety thing. What if the motor was lifting a load and power failed? Brake engages and nothing falls.

 

[RJSakowski]

I have a brake on the z axis of my Tormach mill. It's purpose is to prevent the head from going into free fall when the stepper drive isn't energized. The brake is active with no power applied and is disengaged when the stepper is powered up. This is a requirement when a ball screw is used as it can be back driven.

 

[mksj]

Diode and power 24VDC supply are to operate the brake relay/contactor, activation is by CN1, reverse diode is either separate or can be integrated into the relay. It prevents a reverse voltage spoke when the relay opens and spike can be around 130-150V which can damage a SS switch used by the controller. The relay or contactor uses a separate voltage supply depending on the brake used, this could be a motor brake, and can be significant current. Typically this is switched AC going to a diode bridge which operates a motor brake or can be various voltage and current types.

 

[xbartx]

I have a brake on the z axis of my Tormach mill. It's purpose is to prevent the head from going into free fall when the stepper drive isn't energized. The brake is active with no power applied and is disengaged when the stepper is powered up. This is a requirement when a ball screw is used as it can be back driven.

This is for a lathe spindle and being uneducated about servos, I assumed I needed a brake. The DC motor this is replacing needed one. I now know I don't need one with a servo.

 

[markba633csi]

Now I see the reasoning behind the dual pole relay- if a single pole were to stick closed that would be unsafe. Two poles gives two chances to break the circuit in a deadman system
How much safer? Hard to say without a statistical analysis and my math skills are lame as in duck
Anyhow, the brake coil probably should have a voltage suppressor device across it

 

[Chip Hacket]

Does this look right?

View attachment 510037

Looks good to me! Energizing the control relay activates the brake coil, releasing the physical brake. As others have mentioned, having two poles on the brake coil relay isn’t strictly necessary, but it’s fine if used. The diode is a flyback diode, which protects the drive’s electronics from voltage spikes generated when the magnetic field in the control relay coil collapses after de-energizing.

 

[RJSakowski]

Now I see the reasoning behind the dual pole relay- if a single pole were to stick closed that would be unsafe. Two poles gives two chances to break the circuit in a deadman system
How much safer? Hard to say without a statistical analysis and my math skills are lame as in duck
The brake coil probably should have a voltage suppressor device across it

If the probability of a failure was 1/1.000, the probability of two independent relays both failing is 1/1,000,000. However a double pole relay isn't the same as two independent relays as one set of contacts welding would in all likelihood keep the second set closed as well.

But I will often wire two sets of contacts in parallel on a double pole relay or switch as it increases the reliability of obtaining a contact close . In that mode, the contacts are functioning as independents and the probability of no having a closure is as above so the respective probabilities of having a closure is 999/1,000 vs 999,999/1/000,000 for one set vs two sets of contacts.

 

[Chip Hacket]

If the probability of a failure was 1/1.000, the probability of two independent relays both failing is 1/1,000,000. However a double pole relay isn't the same as two independent relays as one set of contacts welding would in all likelihood keep the second set closed as well.

But I will often wire two sets of contacts in parallel on a double pole relay or switch as it increases the reliability of obtaining a contact close . In that mode, the contacts are functioning as independents and the probability of no having a closure is as above so the respective probabilities of having a closure is 999/1,000 vs 999,999/1/000,000 for one set vs two sets of contacts.

I certainly agree safety standards need to be maintained but many times they go overboard. I've thought a few times it was mainly to keep the safety officers employed and maybe the lawyers?
Rule #999, Where you need to press three buttons simultaneously, while standing on one foot, and singing the national anthem just to reset the fault.

 

[durableoreo]

The colored block is the motor control and the coil is depicted as the same color. I'm guessing the relay is within the control.

Isn't this mainly for safety and holding position without overheating?