This is a fun an very useful project that allows easy access into any door with a deadbolt. I have another version that is used on my garage door and uses the same basic circuit and fobs. The system operates in the RF region at 125 KHz. Fobs are used to actuate one of two relays on the main control board. With each scan the deadbolt toggles - if it is unlocked it locks and the red LED comes on, if locked it unlocks and the green LED comes on. One relay causes the deadbolt motor / mechanism to lock the door, the other causes the door to unlock. A regular key can still be used and the deadbolt can still be locked and unlocked manually if desired. Operating the circuit with the key or manually operating it with the deadbolt knob can cause it to fall out of sync with the controller and indicate locked when it is actually unlocked or vice versa. To correct this just cycle the unit with the pushbutton on the deadbolt housing or flip the deadbolt knob the opposite way. I have thought about adding some limit switches to eliminate this problem. Perhaps in some future version I will implement them. I have been using this project for a couple of months with very few hiccups. It is fun to build and adds a definite 'nerdivity' to my home.

I based the project on a store-bought electronic deadbolt. It was battery operated and had a keypad on the outside to allow entry with a user defined code. I removed all of the electronics from the indoor housing keeping only the electric motor and mechanism. The mechanism has a built-in clutch that prevents damage should the motor remain on for too long when cycling. My motor is set for a cycle time of about 1.25 seconds.

This project is based on the Kwikset Powerbolt Model # 907 15 SMT CP. It cost $69.97 at Home Depot. Almost any battery operated deadbolt will work. It needs some type of clutch mechanism to protect from over-cycling. This was the cheapest unit that Home Depot sold. You may get lucky and find an open box item or a defective unit that can be salvaged. It looks neater than trying to build the motor drive myself.

In future versions I will try to place all components inside the plastic housing where the OEM circuit board was located. There many similar projects you can research on the internet. Do a search for 'RFID ARDUINO DEADBOLT'. There a few on Instructables as well. A Universal RFID Key by drj113 available in Instructables is a good read on RFID theory. Going over this material will be time well spent.


You might also find it helpful, for noise suppression, to put a 100n cap and an 100 ohm resistor in series, across the motor. Also, diodes on the motor wires will help stop nasties. Put the cathodes towards the +ve supply.

jeepdude48507 (author)  steveastrouk1 year ago

The schematic shows a 100n cap across the motor terminals, but I left it off when I soldered the jumper wires. Next time I have it apart I will add one. I am sure there was one installed before I modified. I didn't follow the diodes you mentioned. Could you expand on the idea some more?

If you look at this circuit I did a long time back, you can perhaps see how I did it.

reversing circuit.jpg
jeepdude48507 (author)  steveastrouk1 year ago

I have never seen this circuit before now. It looks like when the motor is running, B+ would be routed to +12 so no current would flow. The negative side would be routed to common with no current flowing. The same thing would happen when the motor is reversed. You mentioned this helps to reduce noise? Is there a common name for this configuration? It looks quite interesting and I would like to learn more. Anything else you may have about this or other comments are welcome. Thanks for the heads up.

The point of this is the condition when the motor is STOPPING. Very large voltages are generated at the terminals of the motor as it stops, THEN the diodes conduct and allow the energy to flow in a loop around the motor - keep the wires short.

These are called flywheel diodes. The RC combo is called either a suppressor or a snubber.

jeepdude48507 (author)  steveastrouk1 year ago

Much like when a relay coil generates a counter EMF when the power is opened. A diode is inserted across the relay coil that bleeds unwanted induced currents from destroying the transistor. In the future I will use this idea. I have seen and used snubbers at work on most relays and motor starters. They come in a single package made by the manufacturer that fit across the coil terminals. Thanks for your input.

The trick is the diodes on a bridge. You can't put the diodes across the motor, because for some directions of the motor, they are forward biased. This is the fix.

jeepdude48507 (author)  steveastrouk1 year ago

I think I got it. Diodes across the motor terminals would be a bad thing. The diodes in the bridge are reverse biased for motor current and forward biased for back EMF. I understand that they must be in a bridge configuration with the AC (~) terminals connected to the motor leads. Connecting a single diode across a DC motor would be bad mojo.

See if this is clearer - you get the 4 diodes you need in a bridge rectifier you can "steal" from a dead PC power supply

2n22221 year ago

I would like to follow your sketch, but I get an error see

RFID_DEADBOLT_125KHz.ino:70: error: 'Toggle' was not
declared in this scope

I have always wanted to do this; Last week I ordered RFID
reader/writer form parallax. I hope ti will work with your wonderful system.


jeepdude48507 (author)  2n22221 year ago

Your right! Thank you for bringing this to my attention. It seems the text portion of instructables is limited. It cut off a large part of my sketch. I am not sure how to attach a file to an instructable yet. If anyone knows please drop me a line. In the mean time if you want to email me at jeepdude48507@yahoo.com I will send you the file. I rarely use this email address as it is my 'junk email' account. I will check it and send the sketch to anyone who wants it until such time as I learn how to attach a file to an instructable..

horphmyre1 year ago

I don't know how many times I've pointed my vehicle remote at my front door, expecting it to unlock. Nice to see one that works.

zx lee1 year ago

You have a neat stripboard layout. What is the tools you used to design the stripboard and the schematic?

jeepdude48507 (author)  zx lee1 year ago

The stripboard was done by manually placing the large components first then the smaller parts were added as it progressed. AutoCAD was used to draw the schematics. I usually draw a schematic before I start to build a project. Then I print the schematic out and write in any changes needed. I also write in notes as I go. In AutoCAD you can save small parts of the drawing in what are called blocks. Blocks can then be used over and over, so with each new drawing I never have to start from scratch.

Great, usually I will use Eagle Cadsoft to design schematics. But it does not have the function you mentioned above.
nodcah1 year ago

Nice! Really professionally done! =D

jeepdude48507 (author)  nodcah1 year ago

Thank You. It was a lot of work, but a lot of fun too.

rjkorn1 year ago

Nice Job.

I made something similar for my garage but i used an old fashioned electrified strike for the door lock and commercial waterproof 125khz reader.

i used eeprom to store the valid cards. now i want to make a menu to allow card updates remotely. I started on a serial menu but using a full size arduino with ethernet or wifi sheild would be nice

jeepdude48507 (author)  rjkorn1 year ago

What type of reader did you use. Are there any pictures of it posted? I would love to see a picture of it.

I want to post it this weekend ill have plenty of pics by then

I used the cheapest readers I could find on ebay....

like these....


Nice! I want to do something like this at my house. Way cool.

jeepdude48507 (author)  craftclarity1 year ago


rjkorn1 year ago

Nice Job.

I made something similar for my garage but i used an old fashioned electrified strike for the door lock and commercial waterproof 125khz reader.

i used eeprom to store the valid cards. now i want to make a menu to allow card updates remotely. I started on a serial menu but using a full size arduino with ethernet or wifi sheild would be nice