Forums

SainSmart relay board

Started by Paul Colby May 11, 2015
I'm trying to switch two 24 volt coaxial switches using a LabJack U6. I 
bought a sainsmart
solid state relay board rated for 240AC @ 2A under the (wrong?) 
assumption that it should
have no issue with switching 24VDC. I'm using the VS output of the 
LabJack (4.9V) to power the
input side of the relay board. I'm switching the logic inputs using the 
DAC 4.8 - 0 outputs
(assuming the 3.3V logic outputs were insufficient). The "on" 
resistance of the relays is
like 4.8Kohms so all the drop is across the relay. Any suggestions 
would be welcome.

Regards
Paul C.
 

Den tirsdag den 12. maj 2015 kl. 01.34.38 UTC+2 skrev Paul Colby:
> I'm trying to switch two 24 volt coaxial switches using a LabJack U6. I > bought a sainsmart > solid state relay board rated for 240AC @ 2A under the (wrong?) > assumption that it should > have no issue with switching 24VDC. I'm using the VS output of the > LabJack (4.9V) to power the > input side of the relay board. I'm switching the logic inputs using the > DAC 4.8 - 0 outputs > (assuming the 3.3V logic outputs were insufficient). The "on" > resistance of the relays is > like 4.8Kohms so all the drop is across the relay. Any suggestions > would be welcome. > > Regards > Paul C.
an AC solidstate relay is probably traic based and will not work for DC get some transistors, resistors and diodes -Lasse
On 2015-05-11 23:58:44 +0000, Lasse Langwadt Christensen said:

> Den tirsdag den 12. maj 2015 kl. 01.34.38 UTC+2 skrev Paul Colby: >> I'm trying to switch two 24 volt coaxial switches using a LabJack U6. I >> bought a sainsmart >> solid state relay board rated for 240AC @ 2A under the (wrong?) >> assumption that it should >> have no issue with switching 24VDC. I'm using the VS output of the >> LabJack (4.9V) to power the >> input side of the relay board. I'm switching the logic inputs using the >> DAC 4.8 - 0 outputs >> (assuming the 3.3V logic outputs were insufficient). The "on" >> resistance of the relays is >> like 4.8Kohms so all the drop is across the relay. Any suggestions >> would be welcome. >> >> Regards >> Paul C. > > an AC solidstate relay is probably traic based and will not work for DC > > get some transistors, resistors and diodes > > -Lasse
Thanks!
On Mon, 11 May 2015 16:58:44 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>Den tirsdag den 12. maj 2015 kl. 01.34.38 UTC+2 skrev Paul Colby: >> I'm trying to switch two 24 volt coaxial switches using a LabJack U6. I >> bought a sainsmart >> solid state relay board rated for 240AC @ 2A under the (wrong?) >> assumption that it should >> have no issue with switching 24VDC. I'm using the VS output of the >> LabJack (4.9V) to power the >> input side of the relay board. I'm switching the logic inputs using the >> DAC 4.8 - 0 outputs >> (assuming the 3.3V logic outputs were insufficient). The "on" >> resistance of the relays is >> like 4.8Kohms so all the drop is across the relay. Any suggestions >> would be welcome. >> >> Regards >> Paul C. > >an AC solidstate relay is probably traic based and will not work for DC > >get some transistors, resistors and diodes > >-Lasse
Logic level mosfets! -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Tue, 12 May 2015 09:34:35 +1000, Paul Colby <paulccolby@paulccolby.com>  
wrote:

> I'm trying to switch two 24 volt coaxial switches using a LabJack U6. I > bought a sainsmart > solid state relay board rated for 240AC @ 2A under the (wrong?) > assumption that it should > have no issue with switching 24VDC. I'm using the VS output of the > LabJack (4.9V) to power the > input side of the relay board. I'm switching the logic inputs using the > DAC 4.8 - 0 outputs > (assuming the 3.3V logic outputs were insufficient). The "on" resistance > of the relays is > like 4.8Kohms so all the drop is across the relay. Any suggestions would > be welcome. > > Regards > Paul C. >
The advice to do the switching with bipolar or mosfet transistors is right but I suspect something else is also going wrong - the SSR should turn on and stay on, while dropping something like 3 volts or less. That would calculate out to 6 ohms.
Den tirsdag den 12. maj 2015 kl. 02.17.21 UTC+2 skrev John Larkin:
> On Mon, 11 May 2015 16:58:44 -0700 (PDT), Lasse Langwadt Christensen > <langwadt@fonz.dk> wrote: > > >Den tirsdag den 12. maj 2015 kl. 01.34.38 UTC+2 skrev Paul Colby: > >> I'm trying to switch two 24 volt coaxial switches using a LabJack U6. I > >> bought a sainsmart > >> solid state relay board rated for 240AC @ 2A under the (wrong?) > >> assumption that it should > >> have no issue with switching 24VDC. I'm using the VS output of the > >> LabJack (4.9V) to power the > >> input side of the relay board. I'm switching the logic inputs using the > >> DAC 4.8 - 0 outputs > >> (assuming the 3.3V logic outputs were insufficient). The "on" > >> resistance of the relays is > >> like 4.8Kohms so all the drop is across the relay. Any suggestions > >> would be welcome. > >> > >> Regards > >> Paul C. > > > >an AC solidstate relay is probably traic based and will not work for DC > > > >get some transistors, resistors and diodes > > > >-Lasse > > Logic level mosfets! >
clamped or avalanche rated and you can skip the diodes but I'm guessing it is less likely to be found in some random junk box -Lasse
Den tirsdag den 12. maj 2015 kl. 02.24.09 UTC+2 skrev David Eather:
> On Tue, 12 May 2015 09:34:35 +1000, Paul Colby <paulccolby@paulccolby.com> > wrote: > > > I'm trying to switch two 24 volt coaxial switches using a LabJack U6. I > > bought a sainsmart > > solid state relay board rated for 240AC @ 2A under the (wrong?) > > assumption that it should > > have no issue with switching 24VDC. I'm using the VS output of the > > LabJack (4.9V) to power the > > input side of the relay board. I'm switching the logic inputs using the > > DAC 4.8 - 0 outputs > > (assuming the 3.3V logic outputs were insufficient). The "on" resistance > > of the relays is > > like 4.8Kohms so all the drop is across the relay. Any suggestions would > > be welcome. > > > > Regards > > Paul C. > > > > The advice to do the switching with bipolar or mosfet transistors is right > but I suspect something else is also going wrong - the SSR should turn on > and stay on, while dropping something like 3 volts or less. That would > calculate out to 6 ohms.
the DAC output might be too wimpy to trigger the relay -Lasse
On 2015-05-12 00:28:14 +0000, Lasse Langwadt Christensen said:

> Den tirsdag den 12. maj 2015 kl. 02.24.09 UTC+2 skrev David Eather: >> On Tue, 12 May 2015 09:34:35 +1000, Paul Colby <paulccolby@paulccolby.com> >> wrote: >> >>> I'm trying to switch two 24 volt coaxial switches using a LabJack U6. I >>> bought a sainsmart >>> solid state relay board rated for 240AC @ 2A under the (wrong?) >>> assumption that it should >>> have no issue with switching 24VDC. I'm using the VS output of the >>> LabJack (4.9V) to power the >>> input side of the relay board. I'm switching the logic inputs using the >>> DAC 4.8 - 0 outputs >>> (assuming the 3.3V logic outputs were insufficient). The "on" resistance >>> of the relays is >>> like 4.8Kohms so all the drop is across the relay. Any suggestions would >>> be welcome. >>> >>> Regards >>> Paul C. >>> >> >> The advice to do the switching with bipolar or mosfet transistors is right >> but I suspect something else is also going wrong - the SSR should turn on >> and stay on, while dropping something like 3 volts or less. That would >> calculate out to 6 ohms. > > the DAC output might be too wimpy to trigger the relay > > -Lasse
I dragged the pos upstairs and hooked it to my lab supply. at vcc of 7 v I still couldn't get the resistance below 3 kohms. I can buy the theory I'm doing something wrong. The board has no marking and they come in three flavors 5V, 10V and 24V. The relays on the board are rated for 5 V so I assume .....
Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:
> Den tirsdag den 12. maj 2015 kl. 01.34.38 UTC+2 skrev Paul Colby: > >> I'm using the VS output of the LabJack (4.9V) to power the input side >> of the relay board.
Per the specs (below), the relay board needs about 20 mA per relay to operate. Are you sure that the LabJack output can supply that much? (40 mA if you're trying to turn two relays on at once.) Also, you should be able to connect the relay board to power and ground, and then jump each individual input to either +5 V or ground to turn that relay on and off. If that doesn't work, figure out why first.
>> I'm switching the logic inputs using the DAC 4.8 - 0 outputs >> (assuming the 3.3V logic outputs were insufficient).
The spec sheet says inputs about 2.5 V should turn the relays on. 0.5 to 2.5 V is "no man's land", and lower than 0.5 V is off.
> an AC solidstate relay is probably traic based and will not work for DC
If Paul has this one http://www.sainsmart.com/8-channel-5v-solid-state-relay-module-board-omron-ssr-4-pic-arm-avr-dsp-arduino.html then yeah... it says "Isolation: Phototriac" for the solid-state relays. Paul could try (carefully) running a small 120 V AC load - like, a night light or small clock radio - on the load side of one of the relays, to find out if the board works at all. Matt Roberds
On 2015-05-12 01:53:40 +0000, mroberds@att.net said:

> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote: >> Den tirsdag den 12. maj 2015 kl. 01.34.38 UTC+2 skrev Paul Colby: >> >>> I'm using the VS output of the LabJack (4.9V) to power the input side >>> of the relay board. > > Per the specs (below), the relay board needs about 20 mA per relay to > operate. Are you sure that the LabJack output can supply that much? > (40 mA if you're trying to turn two relays on at once.) > > Also, you should be able to connect the relay board to power and ground, > and then jump each individual input to either +5 V or ground to turn > that relay on and off. If that doesn't work, figure out why first. > >>> I'm switching the logic inputs using the DAC 4.8 - 0 outputs >>> (assuming the 3.3V logic outputs were insufficient). > > The spec sheet says inputs about 2.5 V should turn the relays on. > 0.5 to 2.5 V is "no man's land", and lower than 0.5 V is off. > >> an AC solidstate relay is probably traic based and will not work for DC > > If Paul has this one > > http://www.sainsmart.com/8-channel-5v-solid-state-relay-module-board-omron-ssr-4-pic-arm-avr-dsp-arduino.html > > > then yeah... it says "Isolation: Phototriac" for the solid-state relays. > > Paul could try (carefully) running a small 120 V AC load - like, a > night light or small clock radio - on the load side of one of the relays, > to find out if the board works at all. > > Matt Roberds
It's the 20-018-901 which is a arduino compatable 4 switch board. The LabJack is showing no sag in voltage so I think the dac (even the 3.3 V logic) is okay. I did some digging and the Triac relay theory may be the root problem. The relay likely needs a zero crossing on the output to turn on which it isn't getting with DC. I'll try testing AC on the output. My guess is this will work fine except AC doesn't do me any good. Building my own BJT cuircit might be fun. I'm pissed that I got the wrong board.