Hello,
do i need a diode if i use this sort of solenoid with a relay?
Setup: arduino 12vdc, 4 relays and 4 solenoids on 12v (2 solenoids won't ever work at the same time)
I used an other solenoid lock without diode and worked fine...
Grossly insufficient information!
What do you mean by "relays"? Do you mean a four relay module for microcontroller interface? Do you have this? Have you used it? Such modules already contain the diodes relevant for the relay coils themselves, but not for any external part.
Are you using the relays to actuate the solenoids? If you want to preserve the contacts on the relays then yes, you need diodes across the solenoid coils. On the other hand, if we knew the solenoid specifications rather than a picture, some cheap FET modules from eBay would likely be able to control them without the intermediate relays given due care with the wiring layout.
I personally think a relay on a small solenoid like that is a bit overkill. All a relay is is a switch made from a solenoid. Like Paul__B was saying, if you've got a relay controller it's got the diodes in it. If you are hooking up any inductor to your circuit you are going to need the diode to prevent current going backwards through it (unless that's what you want, in this circumstance I don't think you do).
I use small solenoids similar to the one pictured and I made a small circuit with a separate power supply, a diode, resistor and the TIP120 to get a digital signal from 3.3V or 5.0V. It ends up costing several cents instead of dollars and you're not essentially using a solenoid to open a solenoid of similar specs.
I would save the relays for something that really needs a lot of current.
OK, real data!
12 V relay with 40 Ohm coil, that is 300 mA - not far different from the relays themselves!
Those relay modules are fine for use with Arduinos - but as I said there are some tricks with the wiring.
These inexpensive modules would be just fine for operating those solenoids from the Arduino (despite some theoretical concerns about the wrong FET).
You would have to add the diode across the solenoid coil.
Ok, so if i understand it correctly, the relays work just fine like this without diode (it's build in) but it's more expensive and overkill.
Cheaper to do without relay and with diode or with cheaper mosfit.
Knowing how much i know about this, for now i'll keep the relays (already have it working with other solenoid and have the code figured out) and will see lateron for version 1.2
Ps this is my current setup
Preamble: I am not an Electrical Engineer
Yes, I think you are understanding for the most part. You can go ahead and hook up your circuit and your Arduino will probably be safe from blowing up.
Without a separate power supply, I don't know that the Arduino can drive enough current to all your solenoids at once. By using the relays you are adding an extra inductor (with basically the same needs to drive it as the actual thing you want to drive, the solenoid).
So for testing purposes I think you are cool to try out driving a solenoid, but for practical purposes I think you might find that you won't be able to drive all of them at once with the hardware you presented.
Epilog: I am not an Electrical Engineer
I am an electrical engineer. You just need a resistor, transistor, and diode for the coil of each solenoid.
Or just one TPIC6C595 or TPIC6B595 and drive all 4.
p.s. a solenoid and relay are virtually electrically identical.
They both use an electromagnet to move an armature.
One pushes ‘contacts’ around, the other performs other arbitrary mechanical ‘work’ with the displacement of the armature.
In a well designed project, there are very few reasons you might need a relay to ‘drive’ a solenoid, other than some peculiar electrical/mechanical isolation, or just to use more power with double the reactive spikes on the supply rails.
Thx i have seperate power supply for solenoids.
I'll read up on this and will test these things later. (so i'll probably be back when in doubt)
CrossRoads:
Or just one TPIC6C595 or TPIC6B595 and drive all 4.
300 mA each?