Thread: Relay Problem

Try putting a small capacitor across the terminals.
One going from positive to earth, and one going from positive to ground.
Try ceramic caps about 0.01uf
Jaycar link

Originally Posted by kiwiken

I want to control my vaccum cleaner using a on-off-on switch and a relay. One of the "on" position's gets it's earth from the spindle relay terminal No5 on the G540, so the vaccum cleaner starts with the spindle.

Is the relay your using to start the vacuum pump 'onboard' ? That is, is it part of the existing system ?

If so, what I do when I have similar problems is to fit another relay, separate to the system.

Use the onboard relay's 'normal open' contact to activate another relay ... Pass the vacuum start circuit thru this 'offboard' relay's normal open contacts.

This provides a degree of separation, especially if using a separate power supply for the vacuum start, and prevents feedback..

If you need a schematic of this let me know.ool bananas ... greg

Issue will be due to inductive 'kickback' when the relay releases. Simple solution is to install a relay accross the relay coil so it is reverse biased (non conductive) when the coil has current flowing through it.

When the current is interupted by opening either the switching on the G540, or the manual switching, the inductance in the relay coil attempts to maintain the current flowing through itself, and generates a large voltage spike which can be injected back through the logic via the power supply rail, interfering with the other logic systems. This is basically the same principle that is used to generate high voltage sparks for petrol engion ignition systems.

With the diode connected accross the coil, as the spike starts to develop, once the voltage reaches 0.6V, the diode conducts, limiting the development of the spike and quenching it. Fitting quenching diodes accross DC energised relays is a standard procedure within the electronics industry. For a smallish relay a 1A, 400V diode is adequate.

If a diode does not help the situation, the next step is to optically isolate the relay. This can be done with an opto isolator chip controlling the original relay with an independantly filtered power supply, or by substituting the original relay with an optical relay, assuming that the load being controlled (vacuum) is an AC load.

Originally Posted by malb

Simple solution is to install a relay across the relay coil so it is reverse biased (non conductive) when the coil has current flowing through it.

Probably obvious to most, but you meant to say install a diode across the relay coil

Agree with Mal. A snubber diode should solve the problem.
An IN4004 diode should do the trick. Very common. Should be easy to find.

Thank you all for your reply's, I will try and get to jarcar during the week
and get some IN4004 diodes.
When I get the diodes and go to fit then what way do the go?
What end of the diode is the positive and to which terminal of the relay would it go to, the "+" or "-" side?

Regards,
Ken

1N4004 or similar diode is a cylinder or globe of epoxy with a wire exiting at each end. There will be a white line around the cylinder or globe near one end. This denotes the anode of the diode which should be connected to the coil terminal with the positive voltage supply. The other end of the diode connects to the coil terminal that you are switching. Keep the leads as short as possible, if possible connect directly to the terminal pins on the relay. Leads, hookup wire etc will limit the damping applied to the spike.

Originally Posted by malb

1N4004 or similar diode is a cylinder or globe of epoxy with a wire exiting at each end. There will be a white line around the cylinder or globe near one end. This denotes the anode

Sorry to be pedantic, but the white line indicates the cathode, but the connection advice is entirely correct as it's being connected reversed-biased, meaning most of the time it doesn't conduct, only when the relay coil is turned off and the collapsing magnetic field through the windings reverses the voltage across the coil, which forward-biases the diode, causing it to short out and absorb the brief reverse voltage spike.

Originally Posted by kiwiken

I want to control my vaccum cleaner using a on-off-on switch and a relay. One of the "on" position's gets it's earth from the spindle relay terminal No5 on the G540, so the vaccum cleaner starts with the spindle. The other "on" position is wired to ground, so I can turn the vaccum cleaner on when the spindle is off. I can get the relay to operate as I intended it to but the problem I have is it sometimes throw up an error with the smoothstepper or causes a e-stop with mach3.
It throws the errors when the relay clicks off, I think I'm getting "noise" from the relay.
The question is what can I use on the relay to stop this, where do I get it from and how do I wire it up.
Regards,
Ken

I just bought a Shark HD CNC Machine two weeks ago. The controller has a plug for turning on my router but I am using an UPS to protect my computer and my controller. My solution was to purchase a solid state relay from Surplussales.com

(KO) SSR-25DA Fotek solid state relay. 24 - 380 vac, 3 - 32 vdc, 25 amp. Screw terminals. 1-3/4" x 2-1/2" x 1". New stock!! 90 day warranty. $15 each - $14 (5+), $12.75 (12+), $11 (25+), $9.50 (100+), $7.99
I picked up a 12 VDC charger at a second hand store for 25 cents and wired it to the control connections on the relay. It works fine as my UPS cannot supply the current required by my router. Let me know if you would like any more info on how I built it. You could use two relays: one for the router and one for the vacuum. Greybearsd75

Hi All,

I rewired my enclosure and fitted the diodes across my relays.
Everything can be turned on and off now without causing my smoothstepper
to have a heart attack.

Thank you all for your help.

Regards,

Kiwiken