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Semi OT- Automotive Turn Signal Flashers

My curious mind wants to learn the operating principle used in many imported automobile turn signal flashers, the kind which increase their flashing rate considerably when a turn signal bulb burns out. Their flashing rate is inversely proportional to the load. That seems like a good idea as it warns the driver that a bulb has gone s outh.

I had some Ss & Gs last night helping youngest son fix the turn signals on his 95 Honda so he could pass state motor vehicle inspection. The right side turn signals, both front and back, were flashing way too fast and rather dimly too.

The bulbs were the right spec and not burned out, so son soon reached the limit of his expertise and sought my help.

The front turn signal bulbs were dual filament 1157s with the "bright" filament used for the turn signal and the "dimmer" one for the marker light.

The problem turned out to be an open connection in the common (grounded) lead to the front right bulb socket.

So, with the marker lamps off the load presented to the flasher from the right front lamp socket was the two filaments of that bulb in series, going to ground through the three paralleled marker lamp filaments on the remaibning three corners of his car.

Fixing a corroded connection on the other end of the "bad" bulb socket's ground lead cured the problem.

So, without my having to obtain and reverse engineer a flasher, what's inside it that makes its flashing rate inversely proportional to load?

Thanks guys,

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.
Reply to
jeff_wisnia
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A lot of them used to use a Siemens chip the part number begins with a 'U', I can't remember the numerical part though.

The data sheet might be in the automotive folder on my archive PC if its that important.

Reply to
ian field

Look up the part number and see what it is called. It might simply be a bi-metal flasher. When you think automotive, think cheap ;-) ...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
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| E-mail Icon at http://www.analog-innovations.com |    1962     |

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Reply to
Jim Thompson

That's why I posted the question here Jim.

I'm familiar with how the bimetalic flashers of yore were constructed, but I couldn't think of an easy way to make a bimetalic flasher with a flash rate inversely sensitive to the load placed on its output. (And also let it deliver nearly full battery voltage to the bulbs.)

Thus, I figured it probably contains a solid state circuit

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.
Reply to
jeff_wisnia

I last did turn signal about 1968. BUT I do recall that bi-metal flashers flash faster when one bulb was dead. I can't remember why :-( ...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

                           LOSE the WUSS
                          BRING BACK BUSH
Reply to
Jim Thompson

Nah, this one is from 1970 and was very common:

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You can make the oscillator load-dependent :-)

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Regards, Joerg

http://www.analogconsultants.com/

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Reply to
Joerg

That's not American-made, and costs 10¢ to manufacture ;-) ...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

                           LOSE the WUSS
                          BRING BACK BUSH
Reply to
Jim Thompson

r
s

st

light.

d)

he

's

be

=A0 =A0 =A0 ...Jim Thompson

less current, less heat, quicker cool off ?

-Lasse

Reply to
langwadt

By George I think You've got it, thanks!

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The lamp current flows through a 30 milliohm shunt and the lower current threshold for switching from the normal flashing rate to one about double that rate is user selectable viaa the value of one resistor.

I'll sleep better tonight.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.
Reply to
jeff_wisnia

All of the chips in my designs start with a 'U'.

Reply to
krw

I thought you did contract work for Bosch ...

My first real exposure to a US car was a Ford Escort. Not the ones made in Cologne. A co-worker was stalled on the side of I405. Drove out there with some tools from the shop. Took a look, no spark, saw coil, almost puked. They hadn't even potted the darn thang. Bare copper looked at me. Of course since this was near Puget Sound it had all become green and corroded away. Oh man ...

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Reply to
Joerg

light.

Two bi-metal strips, each carrying one contact of the flasher switch. One is heated by a resistor to ground in parallel with the signal lamps. The other is connected in series and heated by the lamp current. This second strip moves when heated so as to increase the distance that the first strip must move to make/break the lamp circuit.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com
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It was this kind of thinking that got us in trouble in the first place.
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Reply to
Paul Hovnanian P.E.

I recall bi-metal flashers and their period, not the frequency, went up with a dead lamp....

I found out about the new ones when I used a LED-replacement lamp on my CRX...

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Reply to
David Lesher

light.

Yup. I was vaguely remembering a heater to ground.

Anyone (besides me) remember the under-dash "voltage regulators" that were bi-metal ?:-) ...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

                           LOSE the WUSS
                          BRING BACK BUSH
Reply to
Jim Thompson

light.

In the late '90's

Most of my automotive work was 1962-1973. ...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

                           LOSE the WUSS
                          BRING BACK BUSH
Reply to
Jim Thompson

Ford's mechanical LM7805 used for the gas gauge? GM used a dual coil meter that didn't need a regulated power source.

--
You can\'t have a sense of humor, if you have no sense!
Reply to
Michael A. Terrell

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

The bimetal strip indicator relays flash slower or not at all with reduced load.

Reply to
ian field

light.

I don't recall those "regulators", but during my high school years I worked for a radio shop is San Francisco and installed and repaired plenty of car radios that used vibrator power supplies to create the B+ high voltage for the vacuum tubes.

Those vibrators dissapeared with the next generation of car radios which used vacuum tubes requiring a plate voltage of only twelve volts, but IIRC solid state audio output stages.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.
Reply to
jeff_wisnia

Yep. I designed a chip to drive those for other applications than fuel float... linearizing a two-axis coil system ;-) ...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

                           LOSE the WUSS
                          BRING BACK BUSH
Reply to
Jim Thompson

light.

My '50 Nash had a vibrator power supply and used the field coil of the speaker as the choke.

And it was quite the battery killer when you "parked in the park"... I always parked on a good downhill slope to ensure a rolling start ;-)

Yep. My '61 Renault Dauphine had low plate voltage tubes, plus Delco-Remy Ge "door-knob" transistors in the output. ...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

                           LOSE the WUSS
                          BRING BACK BUSH
Reply to
Jim Thompson

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