Digital keypad requiring relay, but what kind?

[Mishael]

I'll keep this quick. I have a keypad that puts out a 12 VDC pulse when the right code is entered. I want this to control the lights in my shop which are 120 VAC. I know I need a relay and I know it needs to have a control voltage of 12 VDC and a operating voltage of 120 VAC. What I can't figure is which exact relay to get. It needs to be a switching relay that, once the pulse is received, it stays on until another pulse is received. So far, I haven't found anything that specifically states that it does what I want it to. Any suggestions?
Mishael

 

[ronv]

Probably a latching relay. Make sure the pulse is long enough to latch it.

 

[Mishael]

Yes that is what I want.
I actually have the proper control relay module that comes with the keypad and it is properly wired.
It is rated for "5 amps at 24 VDC/VAC with a maximum voltage of 60 VDC" as the documentation claims
Could I run 6 fluorescent tubes @40 watts/ea. off of 120 VAC? i know it says a max of 60 VDC but that's DC...

 

[KeepItSimpleStupid]

NO.

You want an IMPULSE relay **broken link removed** if you want a keypad pulse to turn it on an off.

If you would like to turn it ON with the keypad and off with a button, then use a dual coil latching relay.

Both coil and contact ratings need to be adhered too. It's probably best to use the keypad's relay to activate whatever relay you choose (latch or impulse).

if you need help picking a latching relay, holler.

 

[Mishael]

The relay I have has DIP switches that let me change how the relay reacts. The impulse function does not do what I want it to do while the latching function does.
After my proper wiring and setting, every time I enter the correct code, the relay turns on and stays on and the next proper code entry shuts the relay off. I was just thinking of relaying a relay. What kind of relay do I need now?

 

[KeepItSimpleStupid]

You need a relay that:
1) Is sized and is appropriate for the load
2) the coil voltage has to be within the bounds of what you have to work with.

There are devices called "Lighting Contactors"

(6*40)/120 is the minimum current you need for your six 40 W lamps. They are or can be inductive, so the ratings should be higher or inductive rated. In reality, it has to be within the wiring gauge. e.g 14 AWG, 15 A or 12 AWG 20 A.
30 Amp inductive contactors are readily available. 24 VAC coil is very common and is used in many furnaces.

 

[Boncuk]

Hi Mishael,

you won't need a latching relay for your application.

Just use the pulse of the keypad to clock a flip-flop. The output of the flip-flop should toggle ON/OFF with each arriving pulse.

Use a relay with a coil voltage fitting the keypad's supply voltage and a power rating. (Not below 300W)

Check out the CD4027. (JK-Master-Slave flip-flop)

Boncuk

 

[Reloadron]

The relay I have has DIP switches that let me change how the relay reacts. The impulse function does not do what I want it to do while the latching function does.
After my proper wiring and setting, every time I enter the correct code, the relay turns on and stays on and the next proper code entry shuts the relay off. I was just thinking of relaying a relay. What kind of relay do I need now?

Based on that, I have several Omron relays sitting here. They are 12 VDC coil three pole double throw. The contacts are rated for 250 VAC 10 Amps. The coil current is less than 200 mA (about 160 mA). I also have some solid state relays that should work for your application. The Omron part number is MK3P5-S and they are an older design. If you want one (relay and socket) send a PM and I'll send you one. If it will help you I don't want anything in return. It would likely leave here next Tuesday as we will be off for the weekend and wife sends things from work.

Ron

 

[Mishael]

Well, I have this relay that is attached to the keypad but it does not have the current rating to run lights. After giving it some thought though, I'm thinking of getting a very large power relay and connecting it to the relay in the back of the keypad. I'm starting to be very lost in all this. There are too many suggestions for me to handle! Which is really a good thing to have. For my application, it seems that a latching relay coming out of the keypad is what I need (and also what I currently have) and an impulse relay connected to the latching relay with a control voltage of 12 VDC and an operating voltage of 110-120 VAC, 20 amp.

 

[Reloadron]

You have a relay output from your device. You have it set to "latch" so once you enter a code the output goes to 12 volts DC. So at this point you have a 12 VDC continous signal to work from. You want to power 120 VAC lighting. So what you now need is either another relay where your 12 volt relay output is the slave and an added relay with a 12 volt DC coil becomes the master switching 120 VAC for the lights. Since the 12 VDC out that you have is latched that 12 volts would control another relay. Slave and Master relays. Since your 12 volts out is latched you do not need a latching or impulse relay. All you need is an everyday mechanical relay with a 12 volt DC coil and contacts that can handle the load of your lamps. Contacts that would handle 10 amps AC @ 120 VAC would handle about 1,000 watts of lights. That assumes standard incadescent lamps. You can use any number of relays. The relay you want will likely run about 7 to 10 bucks. Maybe even less for s single pole single throw which is all you need.

Ron

 

[Mishael]

NO WAIT!
It seems that the way the relay works on this keypad, no power is passed through. I'd have to find my voltmeter but the relay apparently acts like a switch (and it can be set NO or NC), which makes sense because the relay can be both AC or DC. In order to use this, I could splice off my 12 VDC line to the keypad and pass it through the normally closed loop to power the relay?
I also want my relay to power my entire shop (which is one 20 amp line) so if I got a 30 amp, 120 VAC relay i should be fine?

 

[Reloadron]

Setting your output relay on your gizmo N/O or N/C is sort of setting it to be forward or reverse acting. That means that if it is set N/O and you punch in the code the N/O contacts close and the N/C contacts open with respect to relay common. Now if there are three relay terminals there should be a common, normally open and a normally closed. Is this what you have? No voltage out? Then yes, you could drive another relay with 12 VDC or for that matter 120 VAC depending on the relay contacts rating in the device you have.

Ron

 

[Mishael]

Yes I have a 3rd wire and it is indeed a common. I would run a 120 VAC line through but the relay is rated at 60 VAC/VDC max. So I need a 30 amp, 120 VAC impulse relay with a control voltage of 12 DC, SPST

 

[Reloadron]

OK, way back in the beginning you mentioned:

The relay I have has DIP switches that let me change how the relay reacts. The impulse function does not do what I want it to do while the latching function does.
After my proper wiring and setting, every time I enter the correct code, the relay turns on and stays on and the next proper code entry shuts the relay off. I was just thinking of relaying a relay. What kind of relay do I need now?

You do not want an impulse relay, you do not need an impulse relay. You want a relay that can handle 30 amps at 120 VAC across its contacts and it needs to have a 12 VDC coil. While 30 amps is quite beefy it is a basic medium power relay. The contacts can be SPST, SPDT DPST or for that matter DPDT since you will only be using one normally open set of contacts.

This is an example of what you want. You would want the model number MGN1C-DC12 the suffix meaning a 12 VDC coil.

That particular relay can be had here through Allied Electronics. Other manufacturers and distributors sell equivalent relays.

A good Google may find you a cheaper relay. One small problem is that as contact ratings increase they tend to come with higher DC coil voltages.

You are sure that you need a 30 amp relay? That is pretty high for a single load lighting relay.

You can also look into SSRs (Solid State Relays) but as the current rating goes up, so does the cost.

Hope that helps
Ron