Controlling Solenoid Valves with ULN2003A, Inrush Current, Arduino

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I want to control a total of five solenoid valves with my Arduino. The solenoid walves operate at 12 volts and have a power consumption of 5 watts per solenoid valve, which equals a current of roughly 420 milliamps.



My idea is to use a ULN2003A transistor array to do this. The ULN2003A datasheet says it supports voltages of up to 50 volts and a maximum current of 500 milliamps per output.



My question is: Is the ULN2003A with its 500 milliamps maximum current rating per output sufficient to reliably switch the solenoid valves? I'm asking because solenoid valves are inductive loads and if I'm not mistaken, they are subject to inrush current that far exceeds the normal current.









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    I want to control a total of five solenoid valves with my Arduino. The solenoid walves operate at 12 volts and have a power consumption of 5 watts per solenoid valve, which equals a current of roughly 420 milliamps.



    My idea is to use a ULN2003A transistor array to do this. The ULN2003A datasheet says it supports voltages of up to 50 volts and a maximum current of 500 milliamps per output.



    My question is: Is the ULN2003A with its 500 milliamps maximum current rating per output sufficient to reliably switch the solenoid valves? I'm asking because solenoid valves are inductive loads and if I'm not mistaken, they are subject to inrush current that far exceeds the normal current.









    share







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      I want to control a total of five solenoid valves with my Arduino. The solenoid walves operate at 12 volts and have a power consumption of 5 watts per solenoid valve, which equals a current of roughly 420 milliamps.



      My idea is to use a ULN2003A transistor array to do this. The ULN2003A datasheet says it supports voltages of up to 50 volts and a maximum current of 500 milliamps per output.



      My question is: Is the ULN2003A with its 500 milliamps maximum current rating per output sufficient to reliably switch the solenoid valves? I'm asking because solenoid valves are inductive loads and if I'm not mistaken, they are subject to inrush current that far exceeds the normal current.









      share







      New contributor




      Chris1309 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      I want to control a total of five solenoid valves with my Arduino. The solenoid walves operate at 12 volts and have a power consumption of 5 watts per solenoid valve, which equals a current of roughly 420 milliamps.



      My idea is to use a ULN2003A transistor array to do this. The ULN2003A datasheet says it supports voltages of up to 50 volts and a maximum current of 500 milliamps per output.



      My question is: Is the ULN2003A with its 500 milliamps maximum current rating per output sufficient to reliably switch the solenoid valves? I'm asking because solenoid valves are inductive loads and if I'm not mistaken, they are subject to inrush current that far exceeds the normal current.







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          3 Answers
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          You need to read the data sheet carefully- the maximum current per output can be closer to 50mA than 500mA, depending on the conditions. See figures 4 and 5 in the datasheet.



          Surge is not an issue with DC solenoids, but you do need to connect the COM to the supply voltage.



          For such high current I would recommend discrete MOSFETs (logic level) and diodes across the solenoids. For example, AO3400A and 1N40005/M5.






          share|improve this answer





























            up vote
            1
            down vote













            The current won't surge as you expect. Because the solenoids are intended for constant application of the rated 12VDC, they are built
            with enough internal resistance to limit the current; the rated
            current is the largest that (with 12V) they will ever have.



            In addition to inductance (which can be subject to nonlinear
            effects), the solenoid has internal resistance, by design.

            Solenoids for AC application with less internal resistance,
            would also limit current according to AC frequency and
            their inductance.



            As a practical matter, the ULN2003A also has thermal limits and (at the
            ground pin) a total-of-all-outputs current that cannot exceed
            2.5A; at 420 mA per section, six solenoids will be too much
            to drive simultaneously.






            share|improve this answer



























              up vote
              1
              down vote













              A few things on solenoids (either relays or valves), since you are using a ULN2003 I'll assume you are going to drive it with a voltage step:



              1. When apply a voltage step, the current will rise until the electro-magnetic force exceeds static friction.

              2. At this point the plunger (for a valve) or the armature (for a relay) will start moving and create back-EMF which will reducing the current as movement accelerates.

              3. Once the movement ends (usually abruptly), back-EMF goes to zero and the current will raise to stall value.

              4. Usually at this point the voltage is reduced (by PWM) to ~40% of initial value as less force is needed to maintain position as opposed to initiate motion (keep in mind that force is linked to current, not voltage).

              Datasheets often specs both values: boost (initiate movement) and hold (maintain position).



              A good rule of thumb is that hold is ~40% of boost.



              By default, I'd assume the power is given in static (where the valve will be most of the time) so the 420mA would be the hold current then you'd need overhead to be able to activate it properly (~800mA).






              share|improve this answer






















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                3 Answers
                3






                active

                oldest

                votes








                3 Answers
                3






                active

                oldest

                votes









                active

                oldest

                votes






                active

                oldest

                votes








                up vote
                2
                down vote













                You need to read the data sheet carefully- the maximum current per output can be closer to 50mA than 500mA, depending on the conditions. See figures 4 and 5 in the datasheet.



                Surge is not an issue with DC solenoids, but you do need to connect the COM to the supply voltage.



                For such high current I would recommend discrete MOSFETs (logic level) and diodes across the solenoids. For example, AO3400A and 1N40005/M5.






                share|improve this answer


























                  up vote
                  2
                  down vote













                  You need to read the data sheet carefully- the maximum current per output can be closer to 50mA than 500mA, depending on the conditions. See figures 4 and 5 in the datasheet.



                  Surge is not an issue with DC solenoids, but you do need to connect the COM to the supply voltage.



                  For such high current I would recommend discrete MOSFETs (logic level) and diodes across the solenoids. For example, AO3400A and 1N40005/M5.






                  share|improve this answer
























                    up vote
                    2
                    down vote










                    up vote
                    2
                    down vote









                    You need to read the data sheet carefully- the maximum current per output can be closer to 50mA than 500mA, depending on the conditions. See figures 4 and 5 in the datasheet.



                    Surge is not an issue with DC solenoids, but you do need to connect the COM to the supply voltage.



                    For such high current I would recommend discrete MOSFETs (logic level) and diodes across the solenoids. For example, AO3400A and 1N40005/M5.






                    share|improve this answer














                    You need to read the data sheet carefully- the maximum current per output can be closer to 50mA than 500mA, depending on the conditions. See figures 4 and 5 in the datasheet.



                    Surge is not an issue with DC solenoids, but you do need to connect the COM to the supply voltage.



                    For such high current I would recommend discrete MOSFETs (logic level) and diodes across the solenoids. For example, AO3400A and 1N40005/M5.







                    share|improve this answer














                    share|improve this answer



                    share|improve this answer








                    edited 1 hour ago

























                    answered 1 hour ago









                    Spehro Pefhany

                    196k4139389




                    196k4139389






















                        up vote
                        1
                        down vote













                        The current won't surge as you expect. Because the solenoids are intended for constant application of the rated 12VDC, they are built
                        with enough internal resistance to limit the current; the rated
                        current is the largest that (with 12V) they will ever have.



                        In addition to inductance (which can be subject to nonlinear
                        effects), the solenoid has internal resistance, by design.

                        Solenoids for AC application with less internal resistance,
                        would also limit current according to AC frequency and
                        their inductance.



                        As a practical matter, the ULN2003A also has thermal limits and (at the
                        ground pin) a total-of-all-outputs current that cannot exceed
                        2.5A; at 420 mA per section, six solenoids will be too much
                        to drive simultaneously.






                        share|improve this answer
























                          up vote
                          1
                          down vote













                          The current won't surge as you expect. Because the solenoids are intended for constant application of the rated 12VDC, they are built
                          with enough internal resistance to limit the current; the rated
                          current is the largest that (with 12V) they will ever have.



                          In addition to inductance (which can be subject to nonlinear
                          effects), the solenoid has internal resistance, by design.

                          Solenoids for AC application with less internal resistance,
                          would also limit current according to AC frequency and
                          their inductance.



                          As a practical matter, the ULN2003A also has thermal limits and (at the
                          ground pin) a total-of-all-outputs current that cannot exceed
                          2.5A; at 420 mA per section, six solenoids will be too much
                          to drive simultaneously.






                          share|improve this answer






















                            up vote
                            1
                            down vote










                            up vote
                            1
                            down vote









                            The current won't surge as you expect. Because the solenoids are intended for constant application of the rated 12VDC, they are built
                            with enough internal resistance to limit the current; the rated
                            current is the largest that (with 12V) they will ever have.



                            In addition to inductance (which can be subject to nonlinear
                            effects), the solenoid has internal resistance, by design.

                            Solenoids for AC application with less internal resistance,
                            would also limit current according to AC frequency and
                            their inductance.



                            As a practical matter, the ULN2003A also has thermal limits and (at the
                            ground pin) a total-of-all-outputs current that cannot exceed
                            2.5A; at 420 mA per section, six solenoids will be too much
                            to drive simultaneously.






                            share|improve this answer












                            The current won't surge as you expect. Because the solenoids are intended for constant application of the rated 12VDC, they are built
                            with enough internal resistance to limit the current; the rated
                            current is the largest that (with 12V) they will ever have.



                            In addition to inductance (which can be subject to nonlinear
                            effects), the solenoid has internal resistance, by design.

                            Solenoids for AC application with less internal resistance,
                            would also limit current according to AC frequency and
                            their inductance.



                            As a practical matter, the ULN2003A also has thermal limits and (at the
                            ground pin) a total-of-all-outputs current that cannot exceed
                            2.5A; at 420 mA per section, six solenoids will be too much
                            to drive simultaneously.







                            share|improve this answer












                            share|improve this answer



                            share|improve this answer










                            answered 2 hours ago









                            Whit3rd

                            4,3851019




                            4,3851019




















                                up vote
                                1
                                down vote













                                A few things on solenoids (either relays or valves), since you are using a ULN2003 I'll assume you are going to drive it with a voltage step:



                                1. When apply a voltage step, the current will rise until the electro-magnetic force exceeds static friction.

                                2. At this point the plunger (for a valve) or the armature (for a relay) will start moving and create back-EMF which will reducing the current as movement accelerates.

                                3. Once the movement ends (usually abruptly), back-EMF goes to zero and the current will raise to stall value.

                                4. Usually at this point the voltage is reduced (by PWM) to ~40% of initial value as less force is needed to maintain position as opposed to initiate motion (keep in mind that force is linked to current, not voltage).

                                Datasheets often specs both values: boost (initiate movement) and hold (maintain position).



                                A good rule of thumb is that hold is ~40% of boost.



                                By default, I'd assume the power is given in static (where the valve will be most of the time) so the 420mA would be the hold current then you'd need overhead to be able to activate it properly (~800mA).






                                share|improve this answer


























                                  up vote
                                  1
                                  down vote













                                  A few things on solenoids (either relays or valves), since you are using a ULN2003 I'll assume you are going to drive it with a voltage step:



                                  1. When apply a voltage step, the current will rise until the electro-magnetic force exceeds static friction.

                                  2. At this point the plunger (for a valve) or the armature (for a relay) will start moving and create back-EMF which will reducing the current as movement accelerates.

                                  3. Once the movement ends (usually abruptly), back-EMF goes to zero and the current will raise to stall value.

                                  4. Usually at this point the voltage is reduced (by PWM) to ~40% of initial value as less force is needed to maintain position as opposed to initiate motion (keep in mind that force is linked to current, not voltage).

                                  Datasheets often specs both values: boost (initiate movement) and hold (maintain position).



                                  A good rule of thumb is that hold is ~40% of boost.



                                  By default, I'd assume the power is given in static (where the valve will be most of the time) so the 420mA would be the hold current then you'd need overhead to be able to activate it properly (~800mA).






                                  share|improve this answer
























                                    up vote
                                    1
                                    down vote










                                    up vote
                                    1
                                    down vote









                                    A few things on solenoids (either relays or valves), since you are using a ULN2003 I'll assume you are going to drive it with a voltage step:



                                    1. When apply a voltage step, the current will rise until the electro-magnetic force exceeds static friction.

                                    2. At this point the plunger (for a valve) or the armature (for a relay) will start moving and create back-EMF which will reducing the current as movement accelerates.

                                    3. Once the movement ends (usually abruptly), back-EMF goes to zero and the current will raise to stall value.

                                    4. Usually at this point the voltage is reduced (by PWM) to ~40% of initial value as less force is needed to maintain position as opposed to initiate motion (keep in mind that force is linked to current, not voltage).

                                    Datasheets often specs both values: boost (initiate movement) and hold (maintain position).



                                    A good rule of thumb is that hold is ~40% of boost.



                                    By default, I'd assume the power is given in static (where the valve will be most of the time) so the 420mA would be the hold current then you'd need overhead to be able to activate it properly (~800mA).






                                    share|improve this answer














                                    A few things on solenoids (either relays or valves), since you are using a ULN2003 I'll assume you are going to drive it with a voltage step:



                                    1. When apply a voltage step, the current will rise until the electro-magnetic force exceeds static friction.

                                    2. At this point the plunger (for a valve) or the armature (for a relay) will start moving and create back-EMF which will reducing the current as movement accelerates.

                                    3. Once the movement ends (usually abruptly), back-EMF goes to zero and the current will raise to stall value.

                                    4. Usually at this point the voltage is reduced (by PWM) to ~40% of initial value as less force is needed to maintain position as opposed to initiate motion (keep in mind that force is linked to current, not voltage).

                                    Datasheets often specs both values: boost (initiate movement) and hold (maintain position).



                                    A good rule of thumb is that hold is ~40% of boost.



                                    By default, I'd assume the power is given in static (where the valve will be most of the time) so the 420mA would be the hold current then you'd need overhead to be able to activate it properly (~800mA).







                                    share|improve this answer














                                    share|improve this answer



                                    share|improve this answer








                                    edited 3 mins ago

























                                    answered 48 mins ago









                                    mcv

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