Hello
I am looking to see what my options are to free up a Digital (C-) port in my CR1000, that is currently being used to trigger a Crydom Relay (7321,D1D07). The relay is being used to control the power supply to a modem , and all other Digital ports are being used for measurements, as is the only available SW12 port.
Is there a way to use the Analog Excitation Port to trigger the same relay ? The trigger voltage is 3.5 V or above, and the VX ports do not exceed 3.5 V. Another issue being whether ExciteV can be used to trigger a relay . I do not have any other analog measurements on the logger.
If the single channel D1D07 is not capable of being used this way, are there other options at a similar price range?
Are there other ways to trigger a relay?
Any information on this would be greatly appreciated.
Thank you
The Vx channels cannot switch a 7321 relay. The maximum excitation voltage is 2.5 volts, which is below the needed voltage to trigger the relay.
Being out of channels, the options available are; add another datalogger, use a multiplexer, or use SDM devices.
Are any of the control ports being used for basic 0-5v monitoring?
If so, can you move one of them to an analog port freeing up a control port for the Crydom?
If needed, you can add a pull down resistor if floating voltage is an issue on the digital line.
Thanks for your input. The digital ports are being mostly being used for COM or SDI-12 inputs. Although one of the sensor does output in analog form, but it is only a shorter version of a data line . The longer data line cannot be read by the analog channel.
I am told that solid state relays that can latch could work using analog signals, but the voltage level of the Vx port is not sufficient to trigger the latching mechanism.
You could use a transistor, pull-up resistor and the CR1000 5V source to achieve triggering voltage levels from a Vx port. The relay would need to be latching-type to work around the fact Vx channels do not support continuous excitation... which might mean you'd need (2) Vx channels: relay on & relay off.
EDIT: I might mean pull-down resistor here (haven't drawn it out). The bigger issue IMO is the latching.
* Last updated by: pokeeffe on 4/23/2015 @ 1:09 PM *
thanks for the tip pokeeffe. Would you mind elaborating this a little more, on how I can use the 5V source, a pull up resistor and a transistor to achieve the trigger voltage?. I am not sure how I could connect them. I imagine this set up could be used to trigger the latching type relay?
gk, Are your SDI-12 sensors on different C ports? If so, you can put more than one SDI-12 sensor into each C port, they need unique addresses. Change the CR1000's program to use the correct address.
This video shows how to change the address:
https://www.campbellsci.com/videos?video=25
* Last updated by: Janet on 4/23/2015 @ 2:01 PM *
I'm thinking about the `Component-Built Relays' section of the CR1000 user manual (8.2.7.3 in current 4/13/15 release). Looking at Fig 101, I think a pull-up/dn resistor is unnecessary (do keep the 1k5 resistor to limit control current; it doesn't affect voltage).
It might void your warranty but if you were so inclined you could make (2) Fig 101 circuits, substituting Vx for C, and select a relay with independent on/off controls. Ensure `ExciteV()` delay is long enough for relay to trigger & latch.
Use Vx channel seems a solution almost unlikely since the Vx go high only during the time required to measure, such as a potentiometer, a PT100 or another, it seems difficult to keep ON a modem with these assumptions.
Maybe one of SDM devices can help you.
Post your program of the CR1000, maybe we can save a control port.
Another option is:
you may also use one or two channels Vx, with a bit of realizing an electronic circuit like flip-flop, so a Vx pulse turns ON and same Vx or other Vx channel pulse turn off, and for best control with an analogue channel you may know sure of which is the state ON or OFF.
I think this allows you to use your solid state relay.
regards
Smile
You may be able to find a commercial, high sensitivity, mechanical latching relay that can be turned on/off with two excitation ports, but you may draw a blank on that. Latching relays only need a pulse to change their state, so that would avoid the problem with the Excitations ports not staying on all the time.
An alternative you could consider is the LR4 relay module we sell where you turn the relays on and off via commands sent from an SDI-12 port. By setting a different SDI-12 address this could be connected in parallel with sensors on the SDI-12 port, with little change to the wiring.
depending on the power draw of the modem, you could control the power with the sw12 port
You would need to do your own selection and product vetting, but there are a variety of relay products on the market that can be controlled using a structured command set over RS-232, RS-485, and Etherent. So datalogger RS-232 to said product, or datalogger with MD485 to one or more relay product, or datalogger with NL peripheral interface to one or more relay product.