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Message |
Daniel J. Stern
Guest
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 Posted:
Tue Feb 08, 2005 1:35 am Post subject:
Circuit design help needed |
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I need help finishing/fixing a circuit design. It isn't/shouldn't be
terribly complex, and I'm not certain whether it's my relative lack of
circuit design experience or simply myopia that's getting in the way of
finishing it. It's an automotive lighting control circuit (relay-fed low
and high beam headlamps with a daytime-running mode).
Not sure if this is the right group in which to be making this request for
help. If not, I'd appreciate a pointer to a more appropriate forum.
The following operational modes are needed:
Engine running, handbrake applied, parking lamps "off": No lights on.
Engine running, handbrake released, parking lamps "off": Low beams and
high beams in series with one another.
Parking lamps "on": No headlamps energized in any way
Headlamps "on": Headlamps function normally, can be switched between low
and high beam, etc.
The difficulty is that I want to control the headlamps via relays to
eliminate voltage drop endemic in many vehicles' factory headlamp
circuitry, per e.g.
http://www.danielsternlighting.com/tech/relays/relays.html .
What we've got so far is at http://dastern.torque.net/DRLcircuit.jpg , but
it's only half-baked yet (where does R1 power come from with headlamp
switch turned off/in DRL mode? How do we discern between "parking lamps
on" and "headlamps on" switch positions so as to kill the DRLs and low and
high beams when the parking lights are on and/or the handbrake warning
lamp switch is closed?)
Any assistance appreciated. I'd rather not get into discussion of
alternative DRL modes; there is a specific reason why I need the circuit
to put the lows and highs in series with one another.
Thanks,
DS
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Pooh Bear
Guest
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| Posted:
Tue Feb 08, 2005 8:40 am Post subject:
Re: Circuit design help needed |
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"Daniel J. Stern" wrote:
| Quote: | I need help finishing/fixing a circuit design. It isn't/shouldn't be
terribly complex, and I'm not certain whether it's my relative lack of
circuit design experience or simply myopia that's getting in the way of
finishing it. It's an automotive lighting control circuit (relay-fed low
and high beam headlamps with a daytime-running mode).
Not sure if this is the right group in which to be making this request for
help. If not, I'd appreciate a pointer to a more appropriate forum.
The following operational modes are needed:
Engine running, handbrake applied, parking lamps "off": No lights on.
Engine running, handbrake released, parking lamps "off": Low beams and
high beams in series with one another.
Parking lamps "on": No headlamps energized in any way
Headlamps "on": Headlamps function normally, can be switched between low
and high beam, etc.
The difficulty is that I want to control the headlamps via relays to
eliminate voltage drop endemic in many vehicles' factory headlamp
circuitry, per e.g.
http://www.danielsternlighting.com/tech/relays/relays.html .
What we've got so far is at http://dastern.torque.net/DRLcircuit.jpg , but
it's only half-baked yet (where does R1 power come from with headlamp
switch turned off/in DRL mode? How do we discern between "parking lamps
on" and "headlamps on" switch positions so as to kill the DRLs and low and
high beams when the parking lights are on and/or the handbrake warning
lamp switch is closed?)
Any assistance appreciated. I'd rather not get into discussion of
alternative DRL modes; there is a specific reason why I need the circuit
to put the lows and highs in series with one another.
|
Where's the problem ?
This has been done 100 times at least.
Reply to my email address ( the rabbit one ) if you need more explanation.
Graham |
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Fred Bloggs
Guest
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| Posted:
Tue Feb 08, 2005 8:27 pm Post subject:
Re: Circuit design help needed |
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| Quote: | I need help finishing/fixing a circuit design. It isn't/shouldn't be
terribly complex, and I'm not certain whether it's my relative lack of
circuit design experience or simply myopia that's getting in the way of
finishing it. It's an automotive lighting control circuit (relay-fed low
and high beam headlamps with a daytime-running mode).
Not sure if this is the right group in which to be making this request for
help. If not, I'd appreciate a pointer to a more appropriate forum.
The following operational modes are needed:
Engine running, handbrake applied, parking lamps "off": No lights on.
Engine running, handbrake released, parking lamps "off": Low beams and
high beams in series with one another.
Parking lamps "on": No headlamps energized in any way
Headlamps "on": Headlamps function normally, can be switched between low
and high beam, etc.
The difficulty is that I want to control the headlamps via relays to
eliminate voltage drop endemic in many vehicles' factory headlamp
circuitry, per e.g.
http://www.danielsternlighting.com/tech/relays/relays.html .
What we've got so far is at http://dastern.torque.net/DRLcircuit.jpg , but
it's only half-baked yet (where does R1 power come from with headlamp
switch turned off/in DRL mode? How do we discern between "parking lamps
on" and "headlamps on" switch positions so as to kill the DRLs and low and
high beams when the parking lights are on and/or the handbrake warning
lamp switch is closed?)
Any assistance appreciated. I'd rather not get into discussion of
alternative DRL modes; there is a specific reason why I need the circuit
to put the lows and highs in series with one another.
|
If I understand you correctly- this should do it. You will have to use
diode logic on the relay control circuits to save a bunch of parts. R2
puts BATT on the high beam lamp, R1 puts BATT on the low beam lamp when
activated and GNDs the filament when not activated. R5 is the DRL mode
control relay, in the deactivated state, it will allow IGN to activate
R2 through the diode, and this throws BATT onto the two headlamps in
series to GND through R1, R3 is open in DRL mode. The diode logic
activates R5 whenever any one of HLSW, PLSW, HBSW are on, preventing DRL
mode, and prevents backflow of DRL control into the HLSW circuit. The
PLSW activates R4 which opens the HLSW circuit. The HLSW circuit
activates R3 which GNDs the headlamp common terminal-allowing normal
operation. In summary then, the parking and headlamp circuits operate
off the BATT circuit and work normally, with the parking circuit
shutting off the headlamp circuit. DRL mode is enabled only when the
ignition circuit is on, controlled by the handbrake switch, and disabled
by either the parking lamp or headlamp switch. Use diodes with 1000V PIV
and minimum 5x the relay coil current rating. It is important to note
that the Bosch 87a terminals are 1/2 the current rating of the 87
terminals, and this is why the headlamp power circuit relays are
arranged so that the 87 terminals take the surge.
View in a fixed-width font such as Courier.
..
.. BATT -------+-------, ,->LB
.. | | |
.. HLSW | R1----------
.. o--||--o---, ,-----|o85 o87 o30|
.. (+) | | | | | |
.. BATT-+ | HLSEL | | |o86 o87a |
.. | PLSW | +---------+ | | -----------+
.. o--||--o | | C H L | | | | |
.. | | ,-----------, | o o o | | | --- ---
.. | | | | +---------+ | | /// ///
.. +------+---|---|--------, | | | | | --------, ,->HB
.. | | | | | | | | '---' | |
.. o R4---------- | | | | R2----------
.. PL |o85 o o | ,-o o o-, o o------------|o85 o30 o87|
.. o | 30 87a| | | | | | | | | |
.. | |o86 | | - - - | - - |o86 |
.. | ---------- | V V V | ^ ^ -----------
.. | | | - - - | - - |
.. --- --- | | | | | | | ---
.. /// /// ,--------|-o--o--o '-o o ///
.. | | | |
.. ,------------' DTL | |
.. | | | | ,---,
.. | | | | | |
.. ,--------------, +---------------' --- |
.. | | | | | | /// |
.. | HBSW | | | | | | LCOM
.. IGN-o--||--o | | | '--------------, | ,->
.. | | | | | | |
.. | R5---------- R3------------
.. o |o85 o o | |o85 o30 o87 |
.. HBL | 30 87a| | |
.. o |o86 | |o86 |
.. | ---------- ------------
.. | | |
.. -- --- ---
.. /// /// ///
..
..
.. BATT Battery (+) Ckt
..
.. IGN Ignition Ckt
..
.. HLSW HeadLampSwitch
..
.. PLSW ParkingLampSwitch
..
.. HBSW HandBrakeSwitch
..
.. PL ParkingLamp
..
.. HBL HandBrakeLamp
..
.. HLSEL HeadLamp HiLo Beam Selector Switch
..
.. DTL Diode Terminal Strip
..
.. HB Headlamp High Beam Terminal
..
.. LB Headlamp Low Beam Terminal
..
.. LCOM Headlamp Common Terminal
..
..
.. Bosch Relay 30-com 87-NO 87a-NC
..
.. 85,86 coil
..
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Daniel J. Stern
Guest
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| Posted:
Wed Feb 09, 2005 8:02 am Post subject:
Re: Circuit design help needed |
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On Tue, 8 Feb 2005, Fred Bloggs wrote:
*snip circuit*
Thanks! I will need to study this and mock it up on the test bench, but
it certainly looks well enough conceived to work. Under what name shall I
credit you? (send me an e-mail if you like, dastern at torque dot net).
Another (private) response to my "Halp!" squawk is this:
http://dastern.torque.net/DRLcandidate.jpg
with explicatory notes thus:
Each side of the car will need a DPDT relay, and you will need a heavy
duty SPST for the low beam power.
Operation:
Car off - relays are in de-energized state. Headlights and high beams
work as normal.
Ignition on, hand brake off. Relays are energized and configure the lamps
to have both filaments in series. The high beam filament is grounded, and
the low beam has +12V. The ground terminal is floating.
Turn on the lights (parking lights or better) and the relays are
de-energized so the headlights and high beams operate normally.
Ignition on, hand brake on, same as lights on -- relays de-energized.
You will notice the HB+ and HB- inputs. Those are for the hand brake.
You will use only one, depending on how the hand brake switches. If it
switches +12V, the you connect to HB+. If it switches to ground, you
connect to HB-. You only use one.
How's this strike you?
Thanks again,
DS
--
Being born on a Class-M planet is like winning the lottery. |
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Fred Bloggs
Guest
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| Posted:
Wed Feb 09, 2005 8:30 pm Post subject:
Re: Circuit design help needed |
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Daniel J. Stern wrote:
| Quote: | On Tue, 8 Feb 2005, Fred Bloggs wrote:
What we've got so far is at http://dastern.torque.net/DRLcircuit.jpg , but
it's only half-baked yet
If I understand you correctly- this should do it.
*snip circuit*
Thanks! I will need to study this and mock it up on the test bench, but
it certainly looks well enough conceived to work. Under what name shall I
credit you? (send me an e-mail if you like, dastern at torque dot net).
|
The circuit is ordinary enough to attribute it to standard relay logic
practice. One detail not contained on the schematic is "quenching" the
relay coil driver circuits- this means suppressing the tendency of the
coil inductance to produce transiently large voltages in the circuit
when its current is abruptly interrupted at turn off. The only relays in
the circuit for which this could be a problem are R4 and R5. Both of
these relays will be quenched by the parallel lamps PL and HBL. As long
as the lamp is rated for greater current than the relay coil, this will
present no problem. The PL is most likely rated for much larger current
than R4 coil- so no quenching is necessary, but the HBL is most likely a
miniature thing and could be damaged by the quenching action. To be on
the safe side, add a diode in parallel with R5 85/86 terminals with
anode to GND- so that makes a 6-diode terminal strip. From what I can
see, most of these Bosch power relays draw under 200mA coil current so
that the diodes can all be the inexpensive 1N4007 type- usually a 3 cent
part.
| Quote: | Another (private) response to my "Halp!" squawk is this:
http://dastern.torque.net/DRLcandidate.jpg
with explicatory notes thus:
Each side of the car will need a DPDT relay, and you will need a heavy
duty SPST for the low beam power.
Operation:
Car off - relays are in de-energized state. Headlights and high beams
work as normal.
Ignition on, hand brake off. Relays are energized and configure the lamps
to have both filaments in series. The high beam filament is grounded, and
the low beam has +12V. The ground terminal is floating.
Turn on the lights (parking lights or better) and the relays are
de-energized so the headlights and high beams operate normally.
Ignition on, hand brake on, same as lights on -- relays de-energized.
You will notice the HB+ and HB- inputs. Those are for the hand brake.
You will use only one, depending on how the hand brake switches. If it
switches +12V, the you connect to HB+. If it switches to ground, you
connect to HB-. You only use one.
How's this strike you?
Thanks again,
DS
--
Being born on a Class-M planet is like winning the lottery.
|
The logic is correct except that the PARK input should mean parking
light switch OR headlamp switch is on. Three drawbacks to this are 1)
Bosch does not seem to offer a DPDT in this automotive relay line- at
least not any that are readily available from the re-sellers- they are
all single pole, and 2) unprotected transistors are too fragile to
survive the potential transients in the automotive enivironment- so that
is just one more headache to deal with, and 3) from what I can gather
from the literature, most of the heavy duty relays have higher current
ratings, like a factor of 2x, for the contacts that make when the coil
is energized, and this is because the contact pressure is much greater
than the de-energized contact makes where the pressure is applied by a
weaker spring force- therefore it is better, not only for current
handling but also vibration resistance, to arrange things so that the
normal headlamp operation uses the relays in the energized state-not the
de-energized state.
I notice that you like to eliminate power line loss feed to the
headlamps, so that you will want to duplicate R1-R2-R3 on each side of
the car- everything else can go in a small enclosure near the switches-
break out a pair of 3-wire harnesses running to each control relay
cluster at the headlamps- one wire to each pin 85 input- you can GND the
pins 86 locally. The under dash control schematic would look something
like this, diodes double off the HLSEL and DRL drive to reduce current
rating and allow possibility that HLSEL is make-before-break:
View in a fixed-width font such as Courier.
..
..
..
.. HLSW
.. o--||--o---,
.. (+) | |
.. BATT-+ | HLSEL
.. | PLSW | +---------+
.. o--||--o | | C H L |
.. | | ,------, | o o o |
.. | | | | +---------+
.. +------+---|---|---, | | | |
.. | | | | | +--------+ | | ,------------R1/85
.. o R4---------- | | '--|--|-|------------R3/85
.. PL |o85 o o | | | | | | ,----------R2/85
.. o | 30 87a| | | | | | |
.. | |o86 | | | ,-----+ | | |
.. | ---------- | | | | | | |
.. | | | | | ,--|--+ | |
.. --- --- | | | | | | | |
.. /// /// | | | | | | | |
.. +--o ,-o o o-, o o o o | +-o o-+
.. | | | | | | | | | | | | | | | |
.. --- - | - - - | - - - - | | - - |
.. /// V | V V V | V V V V | | ^ ^ |
.. - | - - - | - - - - | | - - |
.. | | | | | | | | | | | | | | |
.. o-----o--o--o | o o o o | | o--o |
.. | | | | | | | | | | |
.. | | | | | | '-' | | |
.. ,---|--' DTL | | | '------' | |
.. | | | | | | |
.. | | | | '-----------|----|---R1/85
.. | | '---|--------------|----|---R3/85
.. | | '--------------|----+---R2/85
.. ,--------------, +------------------------'
.. | | | | |
.. | HBSW | | | |
.. IGN-o--||--o | | |
.. | | | |
.. | R5----------
.. o |o85 o o |
.. HBL | 30 87a|
.. o |o86 |
.. | ----------
.. | |
.. -- ---
.. /// ///
..
..
.. BATT Battery (+) Ckt
..
.. IGN Ignition Ckt
..
.. HLSW HeadLampSwitch
..
.. PLSW ParkingLampSwitch
..
.. HBSW HandBrakeSwitch
..
.. PL ParkingLamp
..
.. HBL HandBrakeLamp
..
.. HLSEL HeadLamp HiLo Beam Selector Switch
..
.. DTL Diode Terminal Strip
..
.. Bosch Relay 30-com 87-NO 87a-NC
..
.. 85,86 coil
.. |
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Fred Bloggs
Guest
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| Posted:
Wed Feb 09, 2005 9:49 pm Post subject:
Re: Circuit design help needed |
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Fred Bloggs wrote:
[..snip...]
You don't need those extra diodes off the HLSEL L terminal:
View in a fixed-width font such as Courier.
..
..
..
.. HLSW
.. o--||--o---,
.. (+) | |
.. BATT-+ | HLSEL
.. | PLSW | +---------+
.. o--||--o | | C H L |
.. | | ,------, | o o o |
.. | | | | +---------+
.. +------+---|---|---, | | | |
.. | | | | | +--------+ | +--------------R1/85
.. o R4---------- | | '--|--|--------------R3/85
.. PL |o85 o o | | | | | ,----------R2/85
.. o | 30 87a| | | | | |
.. | |o86 | | | ,-----' | |
.. | ---------- | | | | |
.. | | | | | | |
.. --- --- | | | | |
.. /// /// | | | | |
.. +--o ,-o o o-, o--o | +-o o-+
.. | | | | | | | | | | | | | |
.. --- - | - - - | - - | | - - |
.. /// V | V V V | V V | | ^ ^ |
.. - | - - - | - - | | - - |
.. | | | | | | | | | | | | |
.. o-----o--o--o | o o | | o--o |
.. | | | | | | | | |
.. | | | | | | | | |
.. ,---|--' DTL | | '---------' | |
.. | | | | | | |
.. | | | | '-----|----|---R1/85
.. | | '---|--------------|----|---R3/85
.. | | '--------------|----+---R2/85
.. ,--------------, ,------------------------'
.. | | | | |
.. | HBSW | | | |
.. IGN-o--||--o | | |
.. | | | |
.. | R5----------
.. o |o85 o o |
.. HBL | 30 87a|
.. o |o86 |
.. | ----------
.. | |
.. -- ---
.. /// ///
..
..
.. BATT Battery (+) Ckt
..
.. IGN Ignition Ckt
..
.. HLSW HeadLampSwitch
..
.. PLSW ParkingLampSwitch
..
.. HBSW HandBrakeSwitch
..
.. PL ParkingLamp
..
.. HBL HandBrakeLamp
..
.. HLSEL HeadLamp HiLo Beam Selector Switch
..
.. DTL Diode Terminal Strip
..
.. Bosch Relay 30-com 87-NO 87a-NC
..
.. 85,86 coil
.. |
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