3
\$\begingroup\$

I'm curious why an ignition timing light needs to connect to the battery to work.

I may not be fully understanding how they work, but I'm guessing there's an inductive pick up and that illuminates the bulb.

So couldn't just that inductive kick be enough to light the bulb?

\$\endgroup\$
  • \$\begingroup\$ Show me one without a ground connection. google.ca/… and I'll show you one that uses wireless joule charging from the pulse, not the V+ without ground. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 9 '17 at 16:31
13
\$\begingroup\$

It's for power. The power from the magnetic pickup is very small. It's basically a signal, not something you can run a light from directly. The 12 V and ground connections provide the power. This small signal from the magnetic pickup triggers the strobe to fire, but the strobe is power by the 12 V battery.

| improve this answer | |
\$\endgroup\$
  • \$\begingroup\$ Does the magnetic pickup trigger the strobe by biasing a transistor's gate? \$\endgroup\$ – user140123 Aug 9 '17 at 16:39
  • 1
    \$\begingroup\$ @user: In the timing light I used to have, it was a bipolar transistor that was triggered by the magnetic pickup, so a base but no gate. That transistor then triggered the strobe. While it could be done with a FET, a BJT makes more sense for the requirements. \$\endgroup\$ – Olin Lathrop Aug 9 '17 at 16:52
  • 1
    \$\begingroup\$ Yes. There were self-powered timing lights (they connected to the spark plug wire and to ground) but they just used a little neon bulb and so were exceptionally weak. \$\endgroup\$ – Jamie Hanrahan Aug 9 '17 at 22:25
8
\$\begingroup\$

Back in the olden days, ignition timing lights were neon lamps powered off the ignition pulse. They were so dim as to be almost useless (unless you were into performing engine maintenance at night, with the lights off).

Modern ones simply use the ignition pulse to trigger a bright flash from a lamp that is powered by the 12V vehicle battery.

| improve this answer | |
\$\endgroup\$
5
\$\begingroup\$

You still need bias. The magnetic pickup can't extract power and shouldn't from the ignition wire.

The 12 V and ground lead extracts power from your 12 V system to light up the strobe bulb, triggered by the magnetic pickup signal.

| improve this answer | |
\$\endgroup\$
  • 1
    \$\begingroup\$ So the light is actually powered by the 12v and the pick up just acts like a switch connecting 12v to the bulb? \$\endgroup\$ – user140123 Aug 9 '17 at 16:13
  • \$\begingroup\$ @user140123 Pretty much. There is some circutry in between since it's a zenon flash bulb and not straight 12 V bulb. \$\endgroup\$ – winny Aug 9 '17 at 17:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.