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  1. J

    momentary pcb switch question

    I have a small PCB with 4 momentary pcb small switches the ones that when you press it, it briefly completes the circuit until you let go. There are also some back light LEDs. There is a 6 pin connector on the PCB. Two of the pins on the connector are for the + and - of the LEDs. I've tested...
  2. J

    Amplifying speaker without amp or power supply

    I have a PoE IP telephone which has a mini built in speaker. I've removed the speaker and picture of it is below. It's basically a 8Ohm 1W speaker. I removed this speaker and wired up a bigger 8ohm speaker rated at 20W. Ofcourse it's not receiving 20W because the phone is underpowering it...
  3. J

    LEDs and water and moisture ingress

    I want to use a few 3mm LEDs with holders to provide back light for car door handle. Water and moisture ingress is going to be the biggest problem. But if I was to drill a hole and surface mount the led holder then pop the led in from the rear. Technically is the front some shaped resin bit of...
  4. J

    Adding hardwired auxiliary input to car radio amp

    Looking for some help and advice. My car radio unit has a built in amp and has 8 wires going to 4 pair of speakers. It also supports a 3.5mm audio aux input. However, the 3.5mm aux input is treated as a source and I can only hear it when I'm in that source itself. So if I'm listening to the...
  5. J

    TS to TRS microphone

    My usb sound card requires a TRS microphone and I have a TS mono microphone I just want to test if it actually works before buying a TS to TRS converter. If I wanted to temporarily adapt it with a TRS connector the ground will be the sleeve and the tip will be the same I'm assuming but what will...
  6. J

    3.5mm stereo audio jack

    I have a 3.5mm stereo audio cable cut on one end where I have to directly connect it to a left, right and ground connection. However I'm a little confused as to which pins from the stereo jack are what. From what I understand starting from the base of the 3.5mm jack is the ground and then the...
  7. J

    Speaker & Amp Impedance Question

    I have some 8ohm impedance speakers and I have an amp that has output of either 50W at 4ohm or 40W at 8ohm. If connect two of the 8ohm speakers to the single output in parallel that would make the total impedance 4ohm. 4ohm is something the amp supports but question is will the speaker support...
  8. J

    Wire rating for HID headlight ballast

    I have a 40A 12V relay which I am using to provide a direct +12v feed from car battery to power 2x HID xenon bulbs. The wire from the battery will go from the battery to a waterproof blade type fuse-holder, then it will go to pin 30 of the relay. The output on pin 87 I then need to take to 2x...
  9. J

    NE555 Texas Instruments Pinout

    I have a NE555 by Texas Instruments. According to most of the diagrams the pinout is assumed with the U shaped little groove being facing upwards and then pins 1 to 4 is on the left and 5-8 on the right. I've drawn a basic diagram. Is this the correct pin-out that I drew on the actual chip...
  10. J

    Capacitor and Resistor Question

    I have a set of resistors that i'm sure is supposed to be 1M ohm resistors. When I measure it using a digital multimeter. My multimeter has the following resistance measurement setting: 400, 4K, 40K, 4M, 400M. So I put my multimeter on the 4M setting as that seems the closest to 1M. When I...
  11. J

    Can someone simulate this diagram for me please

    I came across the following diagram on the internet which is suposed to simulate the exact waveform a post catalytic convertor o2 sensor in a car does. I'm not too savy with this stuff and wanted to know if anyone is able to run a simulation of this exact diagram and show me how the output...
  12. J

    Help identify which pins power LED's on PCB

    I have a PCB pictured below that has a 6 pin connector soldered which is at the bottom. Can anyone tell me if there are two pins that are + and - that power the 3 LED's on this PCB? Thank you. Below is the pic:
  13. J

    Help with transient protection

    I need some help and advice on how I can add transient protection on the following setup i've drawn up. On the input of my arduino I have a L7809CV regulator board which can handle voltages from 11 to 25v but as I understand if there is faults with the rectifying diodes on alternator then...
  14. J

    Parallel resistance

    In the following drawing example I have a CANBUS that is terminated on both ends with a 120ohm resistor giving the final ohm reading of 60ohms across the two lines. I want to connect the instrument cluster that also has a 120ohm resistor inside it. This will essentially mean instead of there...
  15. J

    Basic Pulse generation help

    I have a speedometer/instrument cluster from a car that I am doing some bench tests on. I've got the cluster powered up by referring to the pinout diagram. I've got turn signals emulated too. However, I want to emulate speed and according to the pinout diagram, there are two speed related pins...
  16. J

    CANBUS Question

    New to this CANBUS thing and trying to figure some stuff out. Can anyone tell me are all the CAN High and CAN Low signals throughout a cars network all the same? So for example if my instrument cluster has a CAN-H and CAN-L wire. Will running the CAN-H and CAN-L from the OBD port give the same...
  17. J

    12V to 5V 3A converter

    I have the following pictured DC 12v to 5V converter On the input I want to put a inline blade fuse. The output says 5V 3A. I was going to put a 3A fuse on the input but then I'm thinking is the input and output amp rating not going to be different? Seeing as input is 12V does that mean it...
  18. J

    1N5822 diodes

    When using a 1n5822 diode, does a small amount of current still get through the direction it's not supposed to? Enough to power something that works on very few milliamps ? Because when I plug in a multimeter in the direction, it still reads a voltage but if I plug in something like a bulb it...
  19. J

    12v EL glow wire

    I have a 12v EL glow wire. It seems to come with some sort plastic cover at the end. I need to push the cover in to a hole but when doing so it gets tight. Can I remove the cover cap and refit it after I've fished it through a hole? What is the purpose of the end cap? As it comes of easily can I...
  20. J

    Inline fusing 12v feed

    If I have a 12v supply going from a car battery to the common pin of multiple relays and I fuse it with a single correctly rated blade fuse at the battery end, do I need to also put blade fuse at the point of each relay? A few relays will be further back in the cars trunk and few at the front...
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