Fingerprint Module with Door lock Solenoid - Arduino Nano .. Need help - Page 1
Forum section: electronics / projects

author: QLF
author_rank: Contributor
timestamp: January 10, 2020, 08:25:14 am
content: Greeting,Thank you for your support guys.I am a newbie to the Electronics, but I did read for a long time and search but this is my first circuit it may look easy for you but I need help.Here are two schematic and I need them to be joined together with Op protection and reverse voltage protection as well.The project is a Solenoid door lock I will add a Finger Print module operated with Arduino Nano to open it.In fact, the solenoid is operated by normal doorbell intercom, so the project here is to make both ways to open the solenoid the fingerprint module and the intercom.Please note:- The solenoid needs 1.8amp to open.- Reverse voltage protection due to the power will come to Arduino when solenoid opened from the intercom.- I have a TIP122 Transistor if needed.- Arduino Nano will be used in the project.- Pin 9 or any will be used to send a signal to the transistor to pass the power required to open the solenoid.- Over 12v protection for Arduino nano if dual input power source will be used.The scenario:* Normal intercom button should open the solenoid.1- Fingerprint Module read the fingerprint2- Arduino Nano received the data approved then send a signal from pin 9 to transistor tip122 to open3- transistor tip 122 opens and passes the current to open the solenoid.4- Fingerprint Module sleep mode after inactive for specific time.Please try to consider the size of the circuit if possible need to be a small or good size to be placed behind the door of the house.Thanks a lot.Yousif

author: QLF
author_rank: Contributor
timestamp: January 19, 2020, 07:05:54 pm
content: Is it possible to use opto-coupler or reed relay to bridge the intercom push-button? and how can i made the circuit?

author: Marco
author_rank: Super Contributor
timestamp: January 19, 2020, 07:51:49 pm
content: What's the bell? What's the handset? Why are they in series?The transistor is burning 2 Watts when on, it's going to get toasty quite quickly when on (over 100 degrees without a heatsink).It's possible that the intercom button switches a voltage to the high side of the solenoid, but it would be easier if the high side of the solenoid is connected to 24V and the intercom button connects the lower side to ground ... that might be possible by simple rewiring. Then you can put your transistor in parallel with the intercom button.

author: QLF
author_rank: Contributor
timestamp: January 19, 2020, 09:00:03 pm
content: This is the Bell & the handset:The main question is how to add Arduino nano &/to verify the finger prints came from the finger print module which will add in this setup in order to open the solenoid lock through finger print "AND" the button in the headset after the bell is ringed?Its doesn't matter If I will change the whole setup but I need to make this project work without problem.Thank you for reply waiting for your update.

author: ebastler
author_rank: Super Contributor
timestamp: January 19, 2020, 09:55:33 pm
content: I don't think you have drawn the connection between the bell, handset, and solenoid correctly. They are not simply connected in series. Otherwise, the bell would ring whenever you operate the solenoid, and the solenoid would activate whenever someone rings the bell.If you do not fully understand those connections, you probably don't want to mess with them. So connecting your new fingerprint device in parallel with the intercom button is probably not a bad idea. And yes, a small relay is the easiest way to do this, while keeping your Arduino isolated from the 24V.You probably don't want a reed relay though: The common ones can't handle 1.8A, and those which can are expensive. But you can buy cheap conventional relays with a few kOhm coil resistance, which the Arduino can drive directly at 5V. Don't forget the free-wheeling diodes, both on the relay coil (to protect the Arduino from inductive voltage spikes) and on the solenoid (to protect the relay contacts, if the 24V are indeed DC).Taking a step back: When you saidQuoteI assume you mean "OR"? I.e. one can either open the door from inside, if someone is home, OR open it from outside with the right fingerprint?If that is the case, why don't you start with some reliability testing of the fingerprint sensor first, before you even think about connecting it to your door? That's quite a critical application: You cannot tolerate any "false positives", where the system lets some unknown person in, and don't want too many "false negatives", where it does not recognize you when you stand outside without your keys. I would not take it for graned that the finoerprint recognition works well enough.

author: Marco
author_rank: Super Contributor
timestamp: January 19, 2020, 11:00:14 pm
content: You'll need to make a sketch. Something like this :https://create.arduino.cc/projecthub/MissionCritical/how-to-set-up-fingerprint-sensor-with-arduino-ebd543But you still need to connect everything correctly electrically and given your schematic I'm not sure you're grasping quite what that means. There's a limited amount of information which can be communicated in a back and forth on a forum, not the best place for basics. The electrical connections you draw for the handset and bell in your schematic makes no sense. The doorbell subunit has a separate connection to the handset (1 and 2) and shouldn't even be in your schematic.If the phoneset uses either a relay or the switch directly to connect the solenoid, which it probably does, then you can attach the solenoid to the power supply and then connect the other side of the solenoid to one connection on the phoneset (5 or 6) and the other connection on the phoneset (6 or 5) to ground. Your transistor then goes in parallel with the two connections on the phoneset, this what is commonly known as low side switching (which makes things easier, can connect the transistor directly to the arduino with a couple 100 Ohm base resistor). The only protection you then need is a free wheeling diode on the solenoid so the inductive kick doesn't harm the transistor.Are you quite quite sure the solenoid takes 24V? At 1.8A it seems more likely it uses 12V ... which would be nice, because then you could use the 12V directly to power your arduino.

author: QLF
author_rank: Contributor
timestamp: January 22, 2020, 03:04:35 pm
content: Update - 22.01.2020Here is my schematic I tried my best bellow:Should I use a fly-back diode as commented after I cleared the schematic? If yes, Where?Is it required to protect the Arduino or any part of the circuit in this diagram?If the Solenoid used 24v dc in this diagram, will 24vdc reached my nano and burned it? If yes how to protect it?Is the circuit protected from using both way to open the solenoid accidentally by finger print and the push button of the headset? If no how to do that?Please note that this is the first work I made it may need many correction as I am newbie in this world.Yousif

author: Marco
author_rank: Super Contributor
timestamp: January 22, 2020, 05:28:09 pm
content: The doorbell unit only has two connections and is entirely irrelevant, unless the image you posted of the commax isn't actually what you have ...

author: QLF
author_rank: Contributor
timestamp: January 23, 2020, 05:56:52 am
content: Quote from: Marco on January 22, 2020, 05:28:09 pmGreeting,Thank you for your reply.Please ignore the attached commax set and check the diagram I posted yesterday. I cleared everything and the requirement here is to let the transistor to pass the current to open the solenoid after applying 5v to the gate, and if any thing required to protect the circuit or correct it please let me know.Thank you Sir,Yousif

author: Marco
author_rank: Super Contributor
timestamp: January 23, 2020, 06:03:08 pm
content: You number wire connections on the Outside door Bell as if the numbers mean something, which they might if you actually told me the real product number of what you're working with ... but then you just draw the solenoid+power-supply willy nilly without indicating to what number connection they are attached to. It's a mess.The transistor emitter should attach to the negative output of the door strike power supply, the transistor collector should attach to the positive output of the door strike power supply. The transistor should have a 100 Ohm base resistor. You possibly need a diode across the solenoid. The negative output of the door strike power supply should be the ground for your arduino.