Hello,
I am doing a project on arduino UNO, with a couple of limit switches,inductor sensors,hall sensors,2 dual relays and a rf receiver.
I have power the arduino through an external adapter 7.5V, and the 2 dual relay modules through another 5V adapter.
I have connected all the parts as the schematic attached. When i measure with a polymetre the voltage output between VCC and GND i get less than 5V depending on how many turned on modules i have.
Is my schematic correct? The GND of dual relays are not connected anywhere. The GND of the EXTERNAL 5V supply is not connected with arduinos GND.
Every GND shown with the symbol is connected to the arduinos GND.
Is the ROLLER limit switch connection correct or should i connect the pin with 5V .
my main concern is the proximity sensor( proximity sensor link and description which is rated 6-24V. I power it through Vin which is 7.5 V and with the divider im reducing the voltage to 5.7V aproximately so as not to bun the digital pin. IS this reliable?
Is there any problem with the actual current, as the inductor is rated to 150 mA.
Im think of adding 2 more inductive sensors.
should the voltages between 5VCC and GND be about 3,9-4,3 while everything is on?
Thanks in advance
** Subsitute Transmitter with receiver on the schematic. The transmitter is a normal RF controller
should the voltages between 5VCC and GND be about 3,9-4,3 while everything is on?
You are probably over-stressing the Arduino's 5V voltage regulator. Is the regulator chip too hot to touch? Is the 7.5V "holding up"?
...I'm not sure where to "draw the line", but if the voltage goes below 4.7V, something's probably wrong.
Which "module" is drawing the most current?
Are the relay coils being powered through the Arduino board? (It doesn't look like it, but I don't know what relay board you're using.)
Do you have a schematic for the relay board?
Vin which is 7.5 V and with the divider im reducing the voltage to 5.7V aproximately so as not to bun the digital pin
Higher than Vcc (or negative voltages) can damage the Arduino. The resistance (the voltage divider) will help to limit the current, and there are protection diodes inside the ATmega chip so it might be OK. But if you are getting 5.7V when Vcc is ~4V, the protection diode might be blown!
Hi DVDdoug,
thank you for your reply.I'm using a switching adapter, so ive tried 7.5,9 and 12 V and i have the same results when im measuring between gnd and 5VCC on the breadboard.
Moreover if i switch to 12V i have the same drop to abou11.1 if i measure on VIN(12V ) and ground .
The relay coils are not powered through arduino.
can i measure with a polymeter the amper that each module draw?
should i use another DIVIDER with less Voltages? i need those voltages just to trigger the pin so i guess 4 would be enough.
Do i need an optocoupler for the inductor sensor??
The proximity sensor is quite unusable without a data sheet - can you provide a link?
Eventually the NPN type is easier to use?
RepRap seems to use a 5V voltage regulator on the sensor output, for connection to an Arduino input.
As already mentioned, a voltage drop of 0.2V or more is not acceptable on the 5V line. If you already have an additional 5V power supply, use it to power everything or at least the external 5V modules.
You can measure the current drawn by each module, or disconnect all and connect one by one again, and watch the impact on the 5V line.
coffeered:
Thank you for your reply. I'm using a switching adapter, so I've tried 7.5,9 and 12 V and I have the same results when I'm measuring between gnd and 5VCC on the breadboard.
Apparently you have fallen into a common trap.
The regulator on the Arduino board is for supplying power to the ATmega chip, essentially nothing else. If you have a switching adapter and it can be set to 5 V then you set it to 5 V and use it to power the Arduino via its 5 V terminal as well as all your other devices. Forget the "Vin" or "barrel jack", they are essentially useless. The only warning here is to make it impossible for the voltage setting to be changed (hot melt glue).
coffeered:
The relay coils are not powered through Arduino.
I also wonder about the relay power. I can imagine that the relay coils are separated by opto couplers, so that the controller operating voltage is independent from the relay coil voltage. But a simple transistor should serve the same purpose, shouldn't it?
DrDiettrich:
The proximity sensor is quite unusable without a data sheet - can you provide a link?
Eventually the NPN type is easier to use?
RepRap seems to use a 5V voltage regulator on the sensor output, for connection to an Arduino input.
As already mentioned, a voltage drop of 0.2V or more is not acceptable on the 5V line. If you already have an additional 5V power supply, use it to power everything or at least the external 5V modules.
these are the datasheet i found for the proximity sensors. proximity datasheet andproximity info
Drdettrich, i know that npn might be more convenient but i bought pnp .
Do you know the reason of the VOltage drop? the thing is that i also want to understand what is going on, and not only build the actual circuit.
Paul__B:
Apparently you have fallen into a common trap.
The regulator on the Arduino board is for supplying power to the ATmega chip, essentially nothing else. If you have a switching adapter and it can be set to 5 V then you set it to 5 V and use it to power the Arduino via its 5 V terminal as well as all your other devices. Forget the "Vin" or "barrel jack", they are essentially useless. The only warning here is to make it impossible for the voltage setting to be changed (hot melt glue).
Hmmm. So how are they powered?
Paul_B, i thought that if i supply just 5V to the arduino, it will have drops to less than 5V probably due to the cables or some components. I read that recommended is 6-7.5-9V so u will have for sure 5V.
whats the difference if i skip regulator and power the arduino through 5v , wil i have enough protection or no voltage drops?
EDIT: i supplied 5v through arduino pin to power it, i have higher voltage drop, measuring about 3.2V, even without the proximity sensor. Moreover if i supply 5V through the barreljack (regulator ) the situation is even worse down to about 2.6V
i power the relay modules through a second 5V adapter.
DrDiettrich:
I also wonder about the relay power. I can imagine that the relay coils are separated by opto couplers, so that the controller operating voltage is independent from the relay coil voltage. But a simple transistor should serve the same purpose, shouldn't it?
a simple transistor, would serve the same purpose as long as the protection. though if i connect the relays to the 5V of the arduino, it has more voltage drops. and i dont know why!!
TomGeorge:
Are the two relay modules, LOW active logic, that is do you need to put a LOW on the input of the control pin to activate the relay?
Tom...
if i input LOW they turn their leds on, if i input HIGH they turn their leds off
DrDiettrich:
The linked data sheet and info are the same useless crap. I feel like in a video with the crucial question: shall I cut the red or the green wire? :-]
As has been said multiple times: power as many attached modules from external power sources, not from the Arduino.
hahah , I'm sorry but i couldnt find better datasheets!!
in that manner, i have to use 3 different power adapters, as i need one for the arduino, one for the inductor, one for the relay-receiver rf- hall sensor. i want to avoid this as i am using 2 more adapters for 2 actuators i am controlling with the relays!
But do you know why the voltage drop is happening? is it because of the current? Im confused as , if i disconnect the proximity sensor, i still have voltage drop about 0.5 V just with small normal arduino components which dont use enough power.
maybe i connected somthing wrong ? or am I measuring something wrong? (I'm measuring between GND and 5V of arduino)
DrDiettrich:
I also wonder about the relay power. I can imagine that the relay coils are separated by opto couplers, so that the controller operating voltage is independent from the relay coil voltage. But a simple transistor should serve the same purpose, shouldn't it?
Here is the circuit to the relay board. The connections shown on your diagram are correct and the opto-couplers draw minimal power from the Arduino supply.
Yes, a simple transistor (or the simpler modules without the opto-coupler) can be used with a common (and adequate) 5 V power supply to relays and Arduino but circuit layout and lead dress become critical.
coffeered:
Do you know the reason of the Voltage drop? the thing is that I also want to understand what is going on, and not only build the actual circuit.
The voltage drop is because the on-board regulator cannot supple the required current.
coffeered:
Paul_B, I thought that if I supply just 5V to the Arduino, it will have drops to less than 5V probably due to the cables or some components.
I refer you to my original answer. You supply 5 V to the Arduino by connecting a regulated 5 V supply to the 5 V pin on the Arduino and ground.
coffeered:
I read that recommended is 6-7.5-9V so u will have for sure 5V.
That nonsense refers to powering via the "barrel jack" or "Vin" and as I explained, applies only if no other components or modules are deriving significant power from the 5 V pin such as your hall sensor module (which probably is trivial) or your transmitter (which almost certainly is not). You must be careful where you read things. Unfortunately, the long-term posters here are your best source of information.
coffeered:
what's the difference if I skip regulator and power the Arduino through 5V, will I have enough protection or no voltage drops?
EDIT: I supplied 5v through Arduino pin to power it, i have higher voltage drop, measuring about 3.2V, even without the proximity sensor. Moreover if I supply 5V through the barreljack (regulator ) the situation is even worse down to about 2.6V
Which is why you do not attempt to power it through "Vin" or the barrel jack as that puts the regulator in the way.
coffeered:
I power the relay modules through a second 5V adapter.
a simple transistor, would serve the same purpose as long as the protection. though if I connect the relays to the 5V of the Arduino, it has more voltage drops. and I don't know why!!
Of course you do. You cannot supply power for the relay coils from the on-board regulator of the Arduino. It simply will not work. I also note you are "doubling up" on the relays.
coffeered:
if i input LOW they turn their LEDs on, if I input HIGH they turn their LEDs off
That part of the circuit you had correct. The opto-couplers connect to the Vcc terminal, you have to pull them LOW to actuate them. Note that in your setup code, you must digitalWrite the relay pins HIGH before to set them with pinMode to OUTPUT, otherwise they may flash on when you boot up.
You can use the same 5 V supply to power the relays and the Arduino but your wiring becomes important. All supply (5 V) lines must travel as a pair with their respective ground lines, so JD-VCC and ground for the relays come from your 5 V power supply and a separate 5 V and ground pair come from the power supply itself to the Arduino. It may be wise to include a 470 µF capacitor directly across the relay board JD-VCC and ground pins.
Paul__B:
Here is the circuit to the relay board. The connections shown on your diagram are correct and the opto-couplers draw minimal power from the Arduino supply.
Yes, a simple transistor (or the simpler modules without the opto-coupler) can be used with a common (and adequate) 5 V power supply to relays and Arduino but circuit layout and lead dress become critical.
A transistor base or gate draws even less current than the opto LED. I don't see why a common ground will result in critical layout or lead dress. The distance between the relay coil and contact pins is usually bigger than the optocoupler pins distance.
[quote author=Paul__B link=msg=3851792 ]
You can use the same 5 V supply to power the relays and the Arduino but your wiring becomes important. All supply (5 V) lines must travel as a pair with their respective ground lines, so JD-VCC and ground for the relays come from your 5 V power supply and a separate 5 V and ground pair come from the power supply itself to the Arduino. It may be wise to include a 470 µF capacitor directly across the relay board JD-VCC and ground pins.[/quote]
well i just tried this:
First of all, I guess that it does matter, but my normal 5Vrated adapter(which i use for relays) outputs ¬5.2-5.3V(just measured it with my polymetre).
So i plugged the+ and - of the adapter on a breadboard. i got a pair to the arduino5v pin and GND and a pair to the relays. Then from the 5V pin i supplied the whole breadboard. I removed the inductor sensor as in this way it needs more than 6V and as a result a separate power supply.
i measure the voltages and its ¬4.7 again. It does have drop.
coffeered:
What do you mean by saying doubling up?
I gather you are using a twin relay board to actuate both relays at the same time, and a second twin relay board in the same manner.
You will not get 0.3 V drop between one part of the circuit and another unless you are using some very strange connecting wires. Breadboards may have bad connections.
I found out that the voltage drop was due to the BREADBOARD. :o :o :o :o
Likely i found out the problem.
One More question. Can i use a 12V adapter, and with voltage dividers, reduce it to 5V so as to supply everything, the arduino (5v), the relays(5V) ,and the 2 inductors (12V) . the adapters ma will be 1.5mA
coffeered:
I found out that the voltage drop was due to the BREADBOARD. :o :o :o :o
That was becoming obvious.
coffeered:
One More question. Can I use a 12V adapter, and with voltage dividers, reduce it to 5V so as to supply everything, the Arduino (5v), the relays(5V) ,and the 2 inductors (12V) . the adapters ma will be 1.5mA
By "voltage divider" you actually mean a "buck converter". Your 12V adapter will need to be rated at least 1 A, preferably 2 A.
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, I'm sorry but i couldnt find better datasheets!!