1v dc signal to change state of relay

Thread Starter

asus123

Joined Mar 5, 2019
8
Hi,
I am looking to be able to change control a relay by using 1v signal. in order to do this, I am using the controlbyweb x-317.
the goal is: when I set the signal to be higher than 1v, a relay is activated.
when the voltage drops below 1v, the relay is deactivated.

does anyone know an simple way to do this.
ideally I want to just buy a device that I can use right out of the box :)
if not, then I can make one myself :)

thanks in advance for your help.

jim
 

crutschow

Joined Mar 14, 2008
23,544
Not enough info.
  • What is the source of the 1V signal?
  • What is the power supply voltage?
  • What load do you want the relay to switch?
 

Thread Starter

asus123

Joined Mar 5, 2019
8
Thanks sghioto. This looks like something that I can use. I ordered it at Amazon already. Thanks!

  • What is the source of the 1V signal?
  • -- I am using controlbyweb model x-317. Not sure what the output detail is. All I know is that it provide 0-10v dc

  • What is the power supply voltage?
  • -- I can use whatever power supply. 12vdc or 24v or 5v ac or dc. I am flexible on this.

  • What load do you want the relay to switch?
  • -- the load is a tiny 3 pole relay.
I believe what sghioto recommended would work for my need. I will test when amazon delivers the item :)

Thanks for the help :)
Jim
 

MisterBill2

Joined Jan 23, 2018
4,068
It may also work to use a reasonably high gain NPN transistor with the emitter to common and the collector to the relay coil and a supply voltage adequate for the relay. One volt to the base should switch on the transistor and operate the relay. At least in theory that works. It is about as simple a scheme as I can come up with. But it might be that your device supplying that 1 volt is not able to deliver enough current to switch on the transistor. I am not familiar with the thing that you referenced by model number.
 
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Thread Starter

asus123

Joined Mar 5, 2019
8
It may also work to use a reasonably high gain NPN transistor with the emitter to common and the collector to the relay coil and a supply voltage adequate for the relay. One volt to the base should switch on the transistor and operate the relay. At least in theory that works. It is about as simple a scheme ass I can come up with. But it might be that your device supplying that 1 volt is not able to deliver enough current to switch on the transistor. I am not familiar with the thing that you referenced by model number.

Thanks misterbill.
Jim
 

NV64

Joined Feb 15, 2019
32
If 1 V is not enough to control the relay, you can reprogram pin X-317 to 5 V. Judging by the description it is possible.
 

Thread Starter

asus123

Joined Mar 5, 2019
8
Hi NV64,

I am not able to use 5v as the control of my relay since that voltage is too high for my needs.
My goal is to use the x-317 to control a HVAC actuator that relies on 0-10v.
During normal operation, the actuator is controlled by the built-in HVAC controller. when the voltage on the x-317 is above 1v, the actuator would be controlled by the x-317 using a relay that will open the circuit to the built-in HVAC controller and close the circuit to the x-317 to the actuator.

If the relay engaged at 5v, then my damper will automatically be 50% open at minimum when the x-317 engage and that would not work for my needs.

infact, with the item that SG suggested, I would be able to actuate the relay at 0.1v, which would be even better since I would have more control over my actuator :)

to summarized:
when I set the x-317 as 0v, the actuator is controlled by the HVAC controller.
when I set the x-317 to any voltage above 1v, the actuator is mechanically switched to be controlled by the x-317 and the actuator would open at 10%. as I increase the voltage, the actuator would open proportionally to the voltage input.

hope that gives more info on what I am trying to accomplish.

thanks,
Jim
 

NV64

Joined Feb 15, 2019
32
If I understand you correctly, you want to control the drive like this:


In my opinion it is better to manage so:
 

Thread Starter

asus123

Joined Mar 5, 2019
8
Nv64, your top diagram is exactly what I was planning to do.
I have 4 HVAC that I want to be able to override independently of each other even though they are located beside each other.
since the x-317 only has 5 outputs, if I were to follow your suggestion, then I would need a total of 8 outputs which means I would need a 2nd x-317. I don't mind using 2 x x-317 if that would work better.

can you share why option 2 as you suggested would be better?

Thanks,
Jim
 

NV64

Joined Feb 15, 2019
32
can you share why option 2 as you suggested would be better?
1 V - too small for most relays, including solid state. The relay may not work. Or it will turn on/off randomly with the control signal of 1 V. in the second option, you will be able to control the drive in the full range(from the damper is completely closed to the damper is fully open), if you configure the digital output X-317 to 0-10 V.
 

MisterBill2

Joined Jan 23, 2018
4,068
1 V - too small for most relays, including solid state. The relay may not work. Or it will turn on/off randomly with the control signal of 1 V. in the second option, you will be able to control the drive in the full range(from the damper is completely closed to the damper is fully open), if you configure the digital output X-317 to 0-10 V.
1 V - too small for most relays, including solid state. The relay may not work. Or it will turn on/off randomly with the control signal of 1 V. in the second option, you will be able to control the drive in the full range(from the damper is completely closed to the damper is fully open), if you configure the digital output X-317 to 0-10 V.
That is why I suggested adding a transistor to power the relay to do the switching. BUT now I see that there also needs ro be a resistor in series with the transistor base because otherwise the base-emitter diode function will clamp the voltage and not allow it to go much above one volt. so I am suggesting starting with a 2r2K ohm resistor. that will allow the voltage to increase while protecting the transistor. I had not realized that the voltage could rise to ten volts. There would have been a problem. Some experimentation with the value of the resistor may be required.
 

Thread Starter

asus123

Joined Mar 5, 2019
8
At this time I will try the first option in nv64's drawing. I don't mind not getting the full range since I am only missing 1v.
Initially, I wanted to power the relay directly, but since the current on the x-317 output is not big enough, I am going to use the comparator voltage that sghito suggested. I think that would be the easiest for me without needing to try to create my own circuit.
One day when I have time, I will try to implement what MisterBill2 suggest by using a transistor, resistor, etc. I am not familiar enough with electronics to be able to implement MisterBill's suggestion without spending lots of time figuring out the details.

thanks,
jim
 

Thread Starter

asus123

Joined Mar 5, 2019
8
Thanks sghioto. This looks like something that I can use. I ordered it at Amazon already. Thanks!
I believe what sghioto recommended would work for my need. I will test when amazon delivers the item :)
Jim
I just received the item that sghioto recommended and test it. it works exactly as expected!
I am able to changed the voltage to deactivate the relay at 0.2 volts. (better than the 1v I initially requested) I didn't try any lower voltage yet. but at 0.2v, that is good enough already.

Thank you for everyone for your ideas!

Regards,
Jim
 

MisterBill2

Joined Jan 23, 2018
4,068
I just received the item that sghioto recommended and test it. it works exactly as expected!
I am able to changed the voltage to deactivate the relay at 0.2 volts. (better than the 1v I initially requested) I didn't try any lower voltage yet. but at 0.2v, that is good enough already.

Thank you for everyone for your ideas!

Regards,
Jim
I looked at that item and it certainly should work as you require, but it costs a lot more than my method would cost. With the transistor at $0.79 and the resistor at $0.10, if you could live with the lack of adjustment it was a better deal. AND it does look like it is well made.
 

Thread Starter

asus123

Joined Mar 5, 2019
8
MisterBill2, since I only need this for 4 unit, the more costlier part is acceptable. especially since I don't need to try this or that to make it work :) If I were to do a lot of this, then I would definitely go with your suggestion and invest more time to do some trial and error before making thousands of them :)

Again, thank you for your suggestion and help.
 
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