I have a 0-10vdc analog control signal going to an LED driver. The LED drive has 3 inputs - on/off, dim+, dim-. At 0vdc the LED driver is still on but at 10% power. I want to split the control cable signal (0-10vdc, 0-40mA) in parallel and connect the on/off (12vdc,5a) to a relay controlled by the 0-10vdc. I'm trying to source a relay that cuts on at say 1mA and 0.5vdc but can handle a signal up to 10vdc w/o frying? What do i need to do?

 

Use a comparitor and LM311 etc, and set for the voltage you want the relay to operate, you may also set up a 555 for it.
Max.

 

You will need to make something I think. Here is a simple circuit that will turn the relay off below about 1 volt.
I think this relay will do it at 12 volts.
http://www.mouser.com/ds/2/418/NG_SS_108-98002_W_P2-196265.pdf

 

I'm pretty inexperienced so let me make sure I understand what is going on here Rony.

The 12v supply will go to the coil and the input contact on the relay. The transistor is basically closing the circuit when enough power is applied through the signal cable with 22k resistance?

v/r

 

That is correct. I forgot one very important part. A small diode to clamp the relay voltage.

 

transistor? http://www.radioshack.com/product/index.jsp?productId=2062609
relay? http://www.radioshack.com/product/index.jsp?productId=12505678
resistor: http://www.radioshack.com/product/index.jsp?productId=2062331
diode: http://www.radioshack.com/product/index.jsp?productId=2062587

 

You may want to look at a mosfet 2N7000 (fetlington) designed for this kind of application.
Max.

 

Yes the 2N700 would be good - It would move the voltage up a bit, but maybe ok. Oh, I don't see any at Radio Shack.
Those components will be ok, but use a 15K resistor with the 3904 transistor. With that relay it will be a little warm right where it switches, but should be ok.

 

If you want to turn on a relay output based on a +/0-10V or 4-20mA signal, you could use a PLC Programmable Logic Controller and some data acquisition modules to do that. I included an example of some equipment that you could use along with a diagram of how it would work below. You can use one tM-AD8 for the 0-10V input and one tM-AD8C for the 4-20mA input. You can use free Ladder Logic and C Language based HMIWorks development software on a PC first to configure the system to trigger the output based on the inputs. The modules and Touch Screen PLC can be daisy chained over RS-485 cabling with two insulated copper wires. I can help you with this if you want. Let me know. You can use a tM-7561 to communicate with the TPD-280 from a PC over USB cabling. You can use one DIN-KA52F power supply to power all these devices. You can daisy chain the power from the power supply with two insulated copper wires.

TPD-280: $199.00 Touchpad Compact 2.8" Touch Screen Controller PLC with high resolution TFT color touch screen which fits in regular electrical wall-mount outlets, communicable over RS-485. Supports Modbus RTU. Includes HMIWorks Ladder Logic and C language programming and GUI development environment. Supports operating temperatures between -20 ~ +70°C.
http://www.icpdas-usa.com/tpd_280_w.html

tM-AD8: $189.00 8-channel Isolated Analog Voltage Input Module with High Voltage Protection. Communicable over RS-485 and Modbus RTU. Input types include: 0 ~ 500 mV, 0 ~ 1 V, 0 ~ 2.5 V, 0 ~ 5 V, 0 ~ 10 V
http://www.icpdas-usa.com/tm_ad8.html

tM-AD8C: $189.00 8-channel Isolated Current Input Module. Communicable over RS-485 and Modbus RTU. Input types include 0-20 mA and 4-20 mA, supports operating temperatures from -25 °C ~ +75 °C
http://www.icpdas-usa.com/tm_ad8c.html

tM-R5: $99.00 5 channel Form A Relay Output Data Acquisition Module, communicable over RS-485 and Modbus RTU Protocol. Din rail mountable and operates between -25C and 75C.
http://www.icpdas-usa.com/tm_r5.html

Maria Lemone