Safety cutoff switch

 

        Used to modern cars, with state of the art burglar alarms? Well, not on a 1995 Jeep that in fact, has nothing for deterring intruders. That's when a simple solution can be added, using just a toggle switch and few feet of electrical wires.

        This is a simple scratch representation of the ignition circuit in this car. Inserting a switch on wire that feeds power to the ignition coil is a simple way to add some protection for non-authorized engine start.

                This is an electrical diagram for a XJ vehicle, but the YJ circuit should be very similar:

        Find the ignition coil:

        Unplug the connector to the coil, will be easier to splice the wire.

   

        There are two wires coming to this connector, cut the wire that powers the coil and splice it into wires going to the cutoff switch in the cabin. Usually, this wire has colors, or you can check voltage on the pins of removed connector with a volt-meter or a simple test jig that I will show next . Hot wire coming from ignition key will have 12V+ (or light bulb of test tig is lit), while the other pin will not.

In order to test this, you need the car key on the "ON" position (not starting engine). There are 4 positions on a car key:

1) OFF/LOCK

2) ACC - Accessories/UNLOCK

3) ON - Ignition

4) START (temporary)

        Install the cutoff switch in dashboard, hidden but easy access to toggle, connected to the two wires from the splicing in coil connection.

        One thing to note, I often forget that this switch exists and try to start the engine, which will not start, as expected. Then I realize I forgot to turn ON the switch and car starts. If you insist too much with the switch OFF, you may end up discharging the car's battery or before that, introduced too much fuel in intake that engine won't start. If this happen, let the car sit for couple minute for fuel to evaporate.

        

Turn-Parking-Marker lights LED upgrade

        Sounds easy right, just plug and play?

        Not really, this project involved trying few different parts from Amazon, having to get the vehicle electric diagrams in order to study and figure out how to make it work.

        The main reason for issues on this and many other upgrades for this vehicle are due to the old electrical design and parts present in this vehicle.

        Flashing relays, for instance, uses bimetallic strips design, instead of electronic oscillator/timer relays. These thermal driven devices requires minimum currents for operation, in fact, it only works if load is present. The load current drives the oscillating process and it somewhat dictates the oscillation frequency. For instance, loads with lower current will oscillate in lower frequencies while higher currents operates in higher frequencies. 

        Because a minimum load current is required for operation, LED loads draws way less current than incandescent bulbs and it is not enough for these flasher relays to work.

        In this vehicle, flasher relays are used for turn and emergency lights.

        Typical \EM flasher relays:

        How it looks internally:

    

        While electronic flashers are usually smaller and retro compatible for easier replacement.

        Typical electronic flasher:

        

    

  

        For the upgrade to LED lights, two relays had to be replaced with modern electronic parts in order to have all turning and emergency functionalities.

        These are plugged into the fuse tray, located under the dashboard near the steering column.

        

        Replace old flashers with this electronic flasher from Amazon:

        Note that although it fits and plug replace the old relay, the electronic designs require an                additional ground wire, which you can connect to any ground available near the fuse tray, usually any screws docked to the car's metal structure. In my case, I decided to splice and extend this ground wire to give me better options for connection.

Upgraded with the following products:

Electroplating copper

It is done . Successfully copper plated non metal materials, which directly translate into the ability to copper plate through hole in PCB.
In house development that probably took over an year of online research and implementation of:

• Plating constant current DC power supply
• Copper plating solution, from scratch, with distilled water
• Hole surface preparation solution to remove smear during drilling
• Surface activation solution, from scratch, not using palladium based elements.
• Precision drilling drill press, currently been upgraded to a CNC drill

Few pics of accomplished plating:

Simple rock platted in copper.

PCB through hole cross cut.

Micro stepdown Buck converter

Fun project, pretty close to reaching my PCB making capabilities in terms of track size and clearances. Also testing my new built PCB drill which was posted earlier.

The brain of this project is the XL4001 IC which minimizes external components and provide excellent voltage regulation and current protection. Input voltage range is from 4.5V to 40V and output current up to 2A. Switching frequency is around 150khz+-25Khz for regulation. 

The schematic follows the basic application circuit from data sheet, with minor changes to allow an adjustable output voltage.

The current protection is defined by value of RS as follow

Iout=0.155/RS

On the board shown, used a 0.3ohm resistor to set Iout max at about 500mA.

As seen, the schematic calls for a 4pin header connector while the board shown has only 3 pins. Since the ground for the load must be isolated from common ground of input power (isolated by RS), two pins input and 2 pins output are required. The shown board will need a layout correction.

Anyways, tested with 20Vdc input,  output adjustable from 3.3v to 18.5V. However, the max output voltage should not exceed input-3V(input-1.5v as per datasheet).

I also used this same IC for a constant current LED driver with very good results, to be posted in the future.

Step Motor driver Allegro A3977

Running some tests on the A3977 step driver IC, schematic below. Have not been able to make it work yet, if ideas out there please chime in with comments.
Note that some resistors are 00(zero)ohms, used as jumpers since I didn't want to make via on this board (yet developing the drill press).

PCB drill press

Building a PCB drill out of a 12mm linear rail and other material sitting around. Thought of making the big jump to a complete CNC machine, but keeping budget lower for now.
The rails are 12mm diameter with two pillow blocks, the must have parts to achieve some level of precision, specially when making PCB's down to 10mils sizes.
The motor used for the drill is an old DC motor from a cordless drill that operates with around 2.A and the motor driving the slide was purchased from eBay. All is working out of a 12V regulated power supply.
The control circuit is as simple as it can gets, just a position switch to detect and stop the slide at idle position, a foot switch to trigger the drill and few components to provide lower speed on the drill motor while in idle state.
The slide is weight balance by both spring and counter weight system and target selection done with a camera and two mirrors made of a HD current in half.
Below some pics and video.

Video1

Video2