I need a 5vdc relay that can switch 120 vac
11-29-2008, 11:42 AM
#2
RE: I need a 5vdc relay that can switch 120 vac
You are probabaly going to have to cascade them, cause any coil that can switch a contact that big is going to need a lot of power. How much power can your 5v source?
Oh and you should look for a solid state relay as well
Oh and you should look for a solid state relay as well
11-29-2008, 11:43 AM
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RE: I need a 5vdc relay that can switch 120 vac
That is a very large contact rating. Relays are not really used at that type of current. A contactor would be used instead but they tend to be big. What is your application? It would probably be easier to switch through a MOSFET. What voltage are you switching? That would give you the power rating which you need to know to source the FET.
11-29-2008, 12:30 PM
#5
RE: I need a 5vdc relay that can switch 120 vac
how about this: http://cgi.ebay.com/CRYDOM-Solid-State-Relay-SSR-HD6025-10-48-600V-25A_W0QQitemZ290274380865QQcmdZViewItemQQptZBI_Aut omation_Components?hash=item290274380865&_trksid=p 3286.c0.m14&_trkparms=72%3A570|66%3A2|65%3A12|39%3 A1|240%3A1318
Any reason this would not work??
It's going to be my automated way of starting and stopping my lathe spindle. So far I have had to do it by hand switch and the more I getCNC the more lazy I get [X(]
My board for control puts out 5 volts dc on outputs.
Any reason this would not work??
It's going to be my automated way of starting and stopping my lathe spindle. So far I have had to do it by hand switch and the more I getCNC the more lazy I get [X(]
My board for control puts out 5 volts dc on outputs.
11-29-2008, 12:47 PM
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RE: I need a 5vdc relay that can switch 120 vac
Sean,
Here's the part available in the US.
www.jameco.com
Part# 162369 25amp relay 3-32volt input
Dan
Here's the part available in the US.
www.jameco.com
Part# 162369 25amp relay 3-32volt input
Dan
11-29-2008, 01:02 PM
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RE: I need a 5vdc relay that can switch 120 vac
That ebay relay looks like it should work at 25 amps. Is your CNC realy taking 30 amps continuous? It is probably 30A surge, so 25 amps at 600 VAC is plenty.... Remember to add a shunt diode (if the relay does not have it internally)..
11-29-2008, 02:21 PM
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RE: I need a 5vdc relay that can switch 120 vac
Sean,
What you are trying to do is a very poor in design. Fusing of the relay contacts is a very real possibility. Please, Please make sure that your ESTOP will absolutely stop the spindle from turning instantaneously. The last thing you want is the relay to fuse and the ESTOP unable to stop the spindle. Is there a VFD (variable frequency drive) that drives the spindle?
By the way...I am an Electronics Engineer who specializes in automating CNC machines using robots and custom built loading and unloading systems.
What you are trying to do is a very poor in design. Fusing of the relay contacts is a very real possibility. Please, Please make sure that your ESTOP will absolutely stop the spindle from turning instantaneously. The last thing you want is the relay to fuse and the ESTOP unable to stop the spindle. Is there a VFD (variable frequency drive) that drives the spindle?
By the way...I am an Electronics Engineer who specializes in automating CNC machines using robots and custom built loading and unloading systems.
11-29-2008, 03:33 PM
#9
RE: I need a 5vdc relay that can switch 120 vac
A 5V coil is a bit unusual & it will be difficult to find the coil voltage & contact current & voltage rating together in one relay.
If you get stuck you can use 2 relays & a 120V to 24V transformer.
A relay or contactor with a 24V coil is quite common up to any contact current rating you are likely to need.
Use the small relay with the 5V coil to switch the 24 volts from the transformer to the coil of the big relay.
The current draw for the 24V coil of the big relay will be peanuts.
Sodid state relays seem attractive but my experience has been when they fail they fail 'ON'.
- John.
If you get stuck you can use 2 relays & a 120V to 24V transformer.
A relay or contactor with a 24V coil is quite common up to any contact current rating you are likely to need.
Use the small relay with the 5V coil to switch the 24 volts from the transformer to the coil of the big relay.
The current draw for the 24V coil of the big relay will be peanuts.
Sodid state relays seem attractive but my experience has been when they fail they fail 'ON'.
- John.
11-29-2008, 03:49 PM
#10
RE: I need a 5vdc relay that can switch 120 vac
I have an E-stop on the CNC side, and the lathe motor unplugs directly in front of me. I feel pretty secure, the one time I did crash the system, the load on the spindle blew the breaker, so in a sense, there is an automated "STOP".
I agree though, you can't be safe enough when moving this type of equipment in the ways they go!
I agree though, you can't be safe enough when moving this type of equipment in the ways they go!
11-29-2008, 04:46 PM
#11
RE: I need a 5vdc relay that can switch 120 vac
Sean,
you can use an interposing relay setup, use a 5VDC solid state relay to drive the 120 V coil on a motor starter relay that has contacts rated for the HP motor you are using.
I have a box of Crydom SS relays if you need one.
Rich
you can use an interposing relay setup, use a 5VDC solid state relay to drive the 120 V coil on a motor starter relay that has contacts rated for the HP motor you are using.
I have a box of Crydom SS relays if you need one.
Rich
11-29-2008, 08:39 PM
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RE: I need a 5vdc relay that can switch 120 vac
Sean,
I do this stuff everyday (6 axis robots in welding, plasma, & pick-n-place operations) and have a large stockpile of control relays & MCR's that will handle the loads your talking about with no problems. Even though your E-stop circuit is wired thru your CNC controller, you should also wire a leg of it thru your "new" startup circuit so that it drops power to your control relay (the 5V one) at the same time. Don't trust an over-amp condition to stop the spindle motion.
Let me know if you need anything.
Bob
I do this stuff everyday (6 axis robots in welding, plasma, & pick-n-place operations) and have a large stockpile of control relays & MCR's that will handle the loads your talking about with no problems. Even though your E-stop circuit is wired thru your CNC controller, you should also wire a leg of it thru your "new" startup circuit so that it drops power to your control relay (the 5V one) at the same time. Don't trust an over-amp condition to stop the spindle motion.
Let me know if you need anything.
Bob
