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 4 added 1390 characters in body edited Apr 23 at 20:32 Huisman 4,99122 gold badges55 silver badges3030 bronze badges GALVANIC ISOLATION If you needed galvanic isolation, you could use e.g. an optocoupler. However, because your microprocessor and contactor share the same power source, there will not be any galvanic isolation. GROUND LOOPS You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In the schematic you provided it would look like this (I only drew the impedances in the main current paths) Every impedance contributes to a voltage drop. The return current of the contactor flows through Z3, Z4, Z5 and Z6 and causes for each a voltage drop. Now, if your low side driver were close to the actuator and both would be far away from the optocoupler, Z3 would be big. When a big current would flow through the Contactor, it wouldcould cause a not to be neglected voltage drop across Z3. So, while you would think you would drive the low side driver with $$\V_B-V_A\$$ you actually drive it with a lower voltage being $$\V_B-V_A-V_{Z3}\$$ (with $$\V_{Z3}\$$ being the voltage drop across Z3). Do note the use of an optocoupler will not prevent this. Luckily, the current through the contactor is relative small (1.3A) and moreover, the BTS3080EJ has an internal gate driver, so the input of the BTS3080EJ is probably not sensitive to variation in voltage $$\V_B-V_C\$$. STARPOINTS If you still want to avoid the discussed voltage drops, you should be using one (or more) starpoint(s). In the picture above the return current of the contactor flowflows through Z3, Z4, Z5 and Z6, each causing a voltage drop. So, each impedance lifts the ground locally with respect of the 'real' ground defined in the left lower corner. E.g. for the local 'ground' voltages $$\V_C\$$ and $$\V_A\$$ applies $$\V_C > V_A > 0V\$$. By using a starpoint you can get rid off Z3, Z5 and Z6 as shown in the picture below. Z4 does not affect the controlling signals coming from the microprocessor as it has the same (local) ground with the BTS3080EJ. (I removed the optocoupler, but as discussed above). Schematics are just for visualisation. Of course, the real starpoints should be considered in the PCB layout. Hint/additional note Try to keep trace Z4 as small as possible. Z4 could lift the ground of the microprocessor. If the microprocessor gets other (analog) signals wrt 'real' ground as well, Z4 can become quite disturbing. I could have flipped around the DC/DC converter and the 7805 in the schematic such it is closer to the starpoint, but then the schematic probably becomes unreadable. You should consider the use of starpoints and take care of trace lengths in the PCB layout anyway. GALVANIC ISOLATION If you needed galvanic isolation, you could use e.g. an optocoupler. However, because your microprocessor and contactor share the same power source, there will not be any galvanic isolation. GROUND LOOPS You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In the schematic you provided it would look like this (I only drew the impedances in the main current paths) Every impedance contributes to a voltage drop. Now, if your low side driver were close to the actuator and both would be far away from the optocoupler, Z3 would be big. When a big current would flow through the Contactor, it would cause a voltage drop across Z3. So, while you would think you would drive the low side driver with $$\V_B-V_A\$$ you actually drive it with a lower voltage being $$\V_B-V_A-V_{Z3}\$$ (with $$\V_{Z3}\$$ being the voltage drop across Z3). Do note the use of an optocoupler will not prevent this. Luckily, the current through the contactor is relative small (1.3A) and moreover, the BTS3080EJ has an internal gate driver, so the input of the BTS3080EJ is probably not sensitive to variation in voltage $$\V_B-V_C\$$. STARPOINTS If you still want to avoid the discussed voltage drops, you should be using one (or more) starpoint(s). In the picture above the return current of the contactor flow through Z3, Z4, Z5 and Z6, each causing a voltage drop. So, each impedance lifts the ground locally with respect of the 'real' ground defined in the left lower corner. E.g. for the local 'ground' voltages $$\V_C\$$ and $$\V_A\$$ applies $$\V_C > V_A > 0V\$$. By using a starpoint you can get rid off Z3, Z5 and Z6 as shown in the picture below. Z4 does not affect the controlling signals coming from the microprocessor as it has the same (local) ground with the BTS3080EJ. (I removed the optocoupler, but as discussed above). Schematics are just for visualisation. Of course, the real starpoints should be considered in the PCB layout. Hint/additional note Try to keep trace Z4 as small as possible. Z4 could lift the ground of the microprocessor. If the microprocessor gets other (analog) signals wrt 'real' ground as well, Z4 can become quite disturbing. I could have flipped around the DC/DC converter and the 7805 in the schematic such it is closer to the starpoint, but then the schematic probably becomes unreadable. You should consider the use of starpoints and take care of trace lengths in the PCB layout anyway. GALVANIC ISOLATION If you needed galvanic isolation, you could use e.g. an optocoupler. However, because your microprocessor and contactor share the same power source, there will not be any galvanic isolation. GROUND LOOPS You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In the schematic you provided it would look like this (I only drew the impedances in the main current paths) Every impedance contributes to a voltage drop. The return current of the contactor flows through Z3, Z4, Z5 and Z6 and causes for each a voltage drop. Now, if your low side driver were close to the actuator and both would be far away from the optocoupler, Z3 would be big. When a big current would flow through the Contactor, it could cause a not to be neglected voltage drop across Z3. So, while you would think you would drive the low side driver with $$\V_B-V_A\$$ you actually drive it with a lower voltage being $$\V_B-V_A-V_{Z3}\$$ (with $$\V_{Z3}\$$ being the voltage drop across Z3). Do note the use of an optocoupler will not prevent this. Luckily, the current through the contactor is relative small (1.3A) and moreover, the BTS3080EJ has an internal gate driver, so the input of the BTS3080EJ is probably not sensitive to variation in voltage $$\V_B-V_C\$$. STARPOINTS If you still want to avoid the discussed voltage drops, you should be using one (or more) starpoint(s). In the picture above the return current of the contactor flows through Z3, Z4, Z5 and Z6, each causing a voltage drop. So, each impedance lifts the ground locally with respect of the 'real' ground defined in the left lower corner. E.g. for the local 'ground' voltages $$\V_C\$$ and $$\V_A\$$ applies $$\V_C > V_A > 0V\$$. By using a starpoint you can get rid off Z3, Z5 and Z6 as shown in the picture below. Z4 does not affect the controlling signals coming from the microprocessor as it has the same (local) ground with the BTS3080EJ. (I removed the optocoupler, but as discussed above). Schematics are just for visualisation. Of course, the real starpoints should be considered in the PCB layout. Hint/additional note Try to keep trace Z4 as small as possible. Z4 could lift the ground of the microprocessor. If the microprocessor gets other (analog) signals wrt 'real' ground as well, Z4 can become quite disturbing. I could have flipped around the DC/DC converter and the 7805 in the schematic such it is closer to the starpoint, but then the schematic probably becomes unreadable. You should consider the use of starpoints and take care of trace lengths in the PCB layout anyway. 3 added 1390 characters in body edited Apr 23 at 20:27 Huisman 4,99122 gold badges55 silver badges3030 bronze badges IfGALVANIC ISOLATION If you needed galvanic isolation, you could use e.g. an optocoupler. However, sincebecause your microprocessor and contactor useshare the same power source, there will not be any galvanic isolation. YouGROUND LOOPS You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In the schematic you provided it would look like this (I only drew the impedances in the main current paths) Every impedance contributes to a voltage drop. Now, if your low side driver were close to the actuator and both would be far away from the optocoupler, Z3 would be big. When a big current would flow through the Contactor, it would cause a voltage drop across Z3. So, while you would think you would drive the low side driver with $$\V_B-V_A\$$ you actually drive it with a lower voltage being $$\V_B-V_A-V_{Z3}\$$ (with $$\V_{Z3}\$$ being the voltage drop across Z3). Do note the use of an optocoupler will not prevent this. Luckily, the current through the contactor is relative small (1.3A) and moreover, the BTS3080EJ has an internal gate driver, so the input of the BTS3080EJ is probably not that sensitive to variation in voltage $$\V_B-V_C\$$.  IfSTARPOINTS If you still want to avoid the discussed voltage drops in your controlling signals, you should be using one or(or more) starpoint(s). In the picture above the return current of the contactor flow through Z3, Z4, Z5 and Z6, each causing a voltage drop. So, each impedance lifts the ground locally with respect of the 'real' ground defined in the left lower corner. E.g. for the local 'ground' voltages $$\V_C\$$ and $$\V_A\$$ applies $$\V_C > V_A > 0V\$$. Picture toBy using a starpoint you can get rid off Z3, Z5 and Z6 as shown in the picture below. Z4 does not affect the controlling signals coming from the microprocessor as it has the same (local) ground with the BTS3080EJ. (I removed the optocoupler, but as discussed above). Schematics are just for visualisation. Of course, the real starpoints should be attached soonconsidered in the PCB layout. Hint/additional note Try to keep trace Z4 as small as possible. Z4 could lift the ground of the microprocessor. If the microprocessor gets other (analog) signals wrt 'real' ground as well, Z4 can become quite disturbing. I could have flipped around the DC/DC converter and the 7805 in the schematic such it is closer to the starpoint, but then the schematic probably becomes unreadable. You should consider the use of starpoints and take care of trace lengths in the PCB layout anyway. If you needed galvanic isolation, you could use an optocoupler. However, since your microprocessor and contactor use the same power source, there will not be any galvanic isolation. You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In the schematic you provided it would look like this (I only drew the impedances in the main current paths) Every impedance contributes to a voltage drop. Now, if your low side driver were close to the actuator and both would be far away from the optocoupler, Z3 would be big. When a big current would flow through the Contactor, it would cause a voltage drop across Z3. So, while you would think you would drive the low side driver with $$\V_B-V_A\$$ you actually drive it with a lower voltage being $$\V_B-V_A-V_{Z3}\$$ (with $$\V_{Z3}\$$ being the voltage drop across Z3). Luckily, the current through the contactor is relative small (1.3A) and moreover, the BTS3080EJ has an internal gate driver, so the input of the BTS3080EJ is not that sensitive to variation in voltage $$\V_B-V_C\$$. If you still want to avoid voltage drops in your controlling signals, you should be using one or more starpoint(s). Picture to be attached soon GALVANIC ISOLATION If you needed galvanic isolation, you could use e.g. an optocoupler. However, because your microprocessor and contactor share the same power source, there will not be any galvanic isolation. GROUND LOOPS You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In the schematic you provided it would look like this (I only drew the impedances in the main current paths) Every impedance contributes to a voltage drop. Now, if your low side driver were close to the actuator and both would be far away from the optocoupler, Z3 would be big. When a big current would flow through the Contactor, it would cause a voltage drop across Z3. So, while you would think you would drive the low side driver with $$\V_B-V_A\$$ you actually drive it with a lower voltage being $$\V_B-V_A-V_{Z3}\$$ (with $$\V_{Z3}\$$ being the voltage drop across Z3). Do note the use of an optocoupler will not prevent this. Luckily, the current through the contactor is relative small (1.3A) and moreover, the BTS3080EJ has an internal gate driver, so the input of the BTS3080EJ is probably not sensitive to variation in voltage $$\V_B-V_C\$$.  STARPOINTS If you still want to avoid the discussed voltage drops, you should be using one (or more) starpoint(s). In the picture above the return current of the contactor flow through Z3, Z4, Z5 and Z6, each causing a voltage drop. So, each impedance lifts the ground locally with respect of the 'real' ground defined in the left lower corner. E.g. for the local 'ground' voltages $$\V_C\$$ and $$\V_A\$$ applies $$\V_C > V_A > 0V\$$. By using a starpoint you can get rid off Z3, Z5 and Z6 as shown in the picture below. Z4 does not affect the controlling signals coming from the microprocessor as it has the same (local) ground with the BTS3080EJ. (I removed the optocoupler, but as discussed above). Schematics are just for visualisation. Of course, the real starpoints should be considered in the PCB layout. Hint/additional note Try to keep trace Z4 as small as possible. Z4 could lift the ground of the microprocessor. If the microprocessor gets other (analog) signals wrt 'real' ground as well, Z4 can become quite disturbing. I could have flipped around the DC/DC converter and the 7805 in the schematic such it is closer to the starpoint, but then the schematic probably becomes unreadable. You should consider the use of starpoints and take care of trace lengths in the PCB layout anyway. 2 added 618 characters in body edited Apr 23 at 19:37 Huisman 4,99122 gold badges55 silver badges3030 bronze badges If you needed galvanic isolation, you could use an optocoupler. However, since your microprocessor and contactor use the same power source, thisthere will not be any galvanic isolation won't work. You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In your diagramthe schematic you provided it would look like this [picture to be added] Every (I only drew the impedances in the main current paths) Every impedance contributes to a voltage drop. Now Now, if your low side driver were close to the actuator and both currentwould be far away from the optocoupler, Z3 would be big. When a big current would flow through opto is smallthe Contactor, it would cause a voltage drop across Z3. So, while you would think you would drive the low side driver with $$\V_B-V_A\$$ you actually drive it with a lower voltage being $$\V_B-V_A-V_{Z3}\$$ (with $$\V_{Z3}\$$ being the voltage drop across Z3). simple driver andLuckily, the impendance betweencurrent through the contactor would be bigis relative small (1.3A) and moreover, the BTS3080EJ has an internal gate driver, so the input of the BTS3080EJ is not that sensitive to variation in voltage $$\V_B-V_C\$$. YouIf you still want to avoid voltage drops in your controlling signals, you should do this bybe using aone or more starpoint(s). Picture to be attached soon If you needed galvanic isolation, you could use an optocoupler. However, since your microprocessor and contactor use the same power source, this galvanic isolation won't work. You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In your diagram you provided it would look like this [picture to be added] Every impedance contributes to a voltage drop. Now, if your low side driver were close to the actuator and both current through opto is small simple driver and the impendance between contactor would be big, You should do this by using a starpoint. If you needed galvanic isolation, you could use an optocoupler. However, since your microprocessor and contactor use the same power source, there will not be any galvanic isolation. You probably want to prevent ground loops. Wires and PCB traces have an inductance and resistance. You could represent this impedance in every line wire in your diagram between two wire connections. In the schematic you provided it would look like this (I only drew the impedances in the main current paths) Every impedance contributes to a voltage drop. Now, if your low side driver were close to the actuator and both would be far away from the optocoupler, Z3 would be big. When a big current would flow through the Contactor, it would cause a voltage drop across Z3. So, while you would think you would drive the low side driver with $$\V_B-V_A\$$ you actually drive it with a lower voltage being $$\V_B-V_A-V_{Z3}\$$ (with $$\V_{Z3}\$$ being the voltage drop across Z3). Luckily, the current through the contactor is relative small (1.3A) and moreover, the BTS3080EJ has an internal gate driver, so the input of the BTS3080EJ is not that sensitive to variation in voltage $$\V_B-V_C\$$. If you still want to avoid voltage drops in your controlling signals, you should be using one or more starpoint(s). Picture to be attached soon Post Undeleted by Huisman occurred Apr 23 at 19:14 Post Deleted by Huisman occurred Apr 19 at 21:29 1 answered Apr 19 at 21:29 Huisman 4,99122 gold badges55 silver badges3030 bronze badges