I'm looking for some help with hooking up a DPDT relay to my arduino to control a 12v, 4 amp linear actuator. I recently purchased the relay and a 2n3904 transistor to send a 5 volt signal to the coil from the arduino but I can't get it to work. The link for the relay spec sheet is below. I hooked everything up according to: Mechanical Engineering | College of Science and Engineering but that setup is not working. Any help would be appreciated.
That circuit diagram is shamefully bad. Its a university course and they omit the diodes to
protect the circuit from inductive kickback, thus destroying your transistor(s) for you and
possibly your Arduino as well....
Whenever an inductive load is switched some sort of protection circuitry is mandatory. For
DC relays and motors a fly-back diode is typically used - search here for details.
Agreed wholeheartedly. I have a special loathing reserved for inaccurate teaching materials.
You should see my reviews of the TAB Books CET Study Guide 4th Edition, a particularly loathsome book IMHO:
And the Residential Construction Academy Electrical Principles, I'm writing a review of it. Several egregious errors in theory, such as claiming that electricity moves faster than light, nearly instantaneously. Several graphs are drawn incorrectly. The Hall Effect detectors are described incorrectly. Etc.
Hi, you will need another relay, the DPDT will give you forward and reverse, but how are you going to stop it at any mid position?
You don’t say if you are using the TIP120.
And can you post the sketch please?
Can you post a picture of your project and and a CAD or picture of your circuit diagram.Thank you.
Venture - I bought the following actuator: http://www.firgelliauto.com/product_info.php?cPath=87&products_id=376 …I also bought a 12v 4 amp battery and it works fine when I hook the actuator wires to the battery so I know that the power source/actuator is not the issue.
TomGeorge - I have a TIP120 ready to go and I understand the logic of hooking this to the 12v ground current after it passes through the COM part of the relay so I have control over the actuator stopping. I have 12v flowing through the coil to the 2n3904 transistor and when I give 5v to the base pin (from my arduino) I can hear the relay switch but the actuator does not move. I am going to post a picture of my circuit layout. At this point I’m thinking that I either have the relay wired incorrectly or that I need a different relay (but I’m pretty sure this relay should work). Maybe I don’t have something properly grounded and a circuit is not being completed? Also, where should I place diodes?
In regards to code, I’m going to use pushbutton switches and just write a simple program to send signals to the transistors accordingly when the buttons are pushed to flip the relay switch. I don’t currently have any arduino pins hooked up besides power and ground because I’m just trying to get the relay to work first.
there are several different ways of controlling your actuator. Do you need to control speed or set a position?
I'm planning on connecting the actuator to a 50 inch TV to create a TV lift cabinet (already have the furniture) so speed does not really matter. The exact position may matter however depending on the how everything fits together.
A DPDT relay setup that with provisions for external limit switches.