Wow, thank you for the tutorial!

 

You can get away with a smaller relay, saving both physical space and current draw through the transistor (due to the coil resistance). Radio Shack carries a 1A and 5A relay and I think a 3A one too. Also, you can probably save space and parts by using a single fuse off the 12vdc source instead of two, as it's completely unnecessary to have to provide 30A to a remote turn-on lead. Generally, you'll be under 1A unless you have more than 10 devices to turn on.

 

You can get away with a smaller relay, saving both physical space and current draw through the transistor (due to the coil resistance). Radio Shack carries a 1A and 5A relay and I think a 3A one too. Also, you can probably save space and parts by using a single fuse off the 12vdc source instead of two, as it's completely unnecessary to have to provide 30A to a remote turn-on lead. Generally, you'll be under 1A unless you have more than 10 devices to turn on.

Good point, a smaller relay would do just fine.

 

Using a TIP dual darlington device you could eliminate the relay too. I think a TIP102, could be wrong.

 

D'oh!

I thought (hoped) this would be an explanantion of the very mysterious and fabled mechanical time delay circuit...

 

thanks for the tip...

u can do alot of ****s with these li'l relays.

 

i need some help with this.

I am using my stock GM truck H/U (not Bose). I will have two amps to turn on, and I have been told that the remote wire will turn on both just fine without a relay, AND I have been told to use a relay. What's the real deal? i am fine with doing all of my install, but this starts to get into confusing electronics for me.

Any and all help is much appreciated.

 

^^^^ This circuit would not be needed for you. This circuit is for the situation when you have a turn on or off pop. For you all you would need is the relay. Just wire 12v constant to 87, ground 85, remote out of HU to 86 and 30 would go to your amps. With a stock head unit I would probably do it to be safe. With aftermarket you can usually do 2 amps safely, 3 amps is hit or miss depending on the HU and draw from the amps and any more than 3 amps I would use a relay.

 

Amp triggers are voltage sensing designs with a very high input impedance. If it puts out 12V and the wire's not broke then I'm sure the requirements for a relay would be nil. Now if the OP were trying to turn on fans/bling/etc it would be a different story.

Chad

 

Cool. I guess what I wanted to avaoid, was having the turn on wire work for some time and then burn out the transistor or whatever inside the HU at a later date.

I was thinking about using Navone's solid state switch:
http://www.davidnavone.com/detail.asp?PRODUCT_ID=N-TRIG-LO

 

why has noone mentioned wiring a capacitor across the relay coil?

on an unrelated note, does anyone know the ballpark minimum voltage is to hold the coil closed on a standard bosch relay?

 

on an unrelated note, does anyone know the ballpark minimum voltage is to hold the coil closed on a standard bosch relay?

Pulling this out of my ass, but...

Lookie here:
http://www.components.omron.com/components/web/pdflib.nsf/0/E6C4C0E4A0A85DDF85257201007DD648/$file/D20G8JR1005.pdf

In the data sheet the parameters you are looking for are pull in voltage and dropout voltage.


IMHO you'll want a strong pull-in voltage to preserve contact life (keep'em from bouncing and pitting). The minimum pull-in voltage for this style relay is typically 8V. However, I would bump that up to at least 10V. However, once pulled in, voltage can be reduced down to about 6V to hold the contacts on. You'll notice the datasheet I linked mentioned approx 1V dropout. I don't believe that. I can see contacts bouncing like wild.

How do you initiate a turn on at 10V and then drop to 6V (or whatever) once on? Fuel injectors do this to preserve their life (reduces power dissipation and thus heat). A number of IC manufactures sell a chip that does this for you. Just go to ST, Infineon, NXP, etc... and search uner the term fuel injector.

Just out of curiosity, why were you asking?

Ge0

 

I built one of these to fix a turn on noise from my amp and I'm having a little problem with it. It works fine as a turn off delay but it doesn't delay the turn on at all which is the exact opposite of what I need it to do. Does anyone know how to make one of these that will delay the turn on?

 

 

good thread

 

not the best circuit, but it does remove a resistor.

the more common way to do this is with a common emitter amplifier, or a common source amplifier.

the more common delay on/off will be based on the attached pic.

in this circuit, at turn on, C1 is charge via R2. if optional diode D2 is installed, then C1 is charged by R4||R2. This allows inrush limiting if C1 is made large. the D2+R3 parts will cause the relay to turn on fast.

as C1 charges, it will reach the Vth of the MOSFET M1, shortly after, it will be able to turn M1 fully on, and K1 will engage.

When ACC is removed, C1 will discharge through R2+R1, eventually reaching Vth and turning off K1. Again, addition of the D2 diode will allow a faster turn off action.

Turn on and turn off times will not be equal in this circuit because the gate of M1 will turn on around 4V, but will charge to 12V. as such it must discharge 8V to turn off, but only charge 4V to turn on.

Diode D1 is the standard flyback diode designed to allow current flowing in K1 to natually stop flowing, instead of suddenly trying to break the magnetic field and causing high voltage spikes across M1.

this circuit can be simplified, or made more complex to acheive desired results.

 

for the case of a turn on delay with no turn off delay, i suggest the attached.

when Acc is engaged, the gate of M1 will charge to 12V, and M1 will engage*, but M2's gate is delayed by the time required to charge C1 to Vth through R1. Once M2 starts to conduct, M1 will also turn on, and K1 will engage.

when Acc is disengaged, the gate of M2 will stay high, discharging through R1+R2. M1's gate will quickly drop below Vth if R1 is much larger then R2. this will quickly turn the circuit off.

because this circuit uses mosfets, and is a common source design, the transistors will dissipate very little heat.


suggest making Vcc*R2/(R1+R2) < Vth, which means
Vcc/Vth < R1/R2 + 1
or:
R1 > R2*(Vcc/Vth - 1)

suggest making R2 10kohm. if a 2n7000 is used, Vth will be around 2V. meaning giving R1 > 10k(12/2 - 1), R1 >50k.

time delay will be based on the size of R1 and C1:
Vgs = Vcc - Vcc e^-t/R1C1
for Vgs = Vth
Vth/Vcc = 1 - e^-t/R1C1
1 - Vth/Vcc = e^-t/R1C1
ln(1-Vth/Vcc) = -t/R1C1
t = -R1*C1*ln(1-Vth/Vcc)

since we know R1 > 50k:
C1 > -t/(R1*ln(1-Vth/Vcc))

for a sample 1 second delay:
C1 > -1/(50k*ln(1-2/12))
C1 > 109uF

Hmm, 109uF is attainable, but if I wanted say, 60 seconds of delay, this would not bode well, and I'd be forced to raise R1, which i can do without much penelty.


* rather will be engageable.


edit -- and if you wanted a turn off delay with minimal turn on delay, you could place M1, M2 in parallel instead of series.

Keep in mind, that this circuit should not be turned on/off at a high rate, as C1 will need to discharge. for such apps, a speedup diode as shown above would be needed to clear C1 at a faster rate. if a short turn off delay is acceptable, M1 might be omitted and the speedup diode used.

 

Forgive my noob-ness.... but what is the purpose of this circuit?

 

to eliminate turn off pops or turn on pops that are caused by an entire series of equipment that powers on in a "less than optimal" order.

not uncommon in complex systems.
http://www.selectronic.fr/article.asp?article_ref_entier=70.2750-5US

of course, why should anyone pay $200 euro when a creative installer can buy $5 worth of parts above (and probably has 90% of the parts laying around for free anyways) for each piece of gear they have and start swapping out caps for timing till they have the order right anyways?

And even farther, chances are good that there are only gonna be two pieces of gear in the car that "fight" over turn on and turn off speed anyways (one signal processor, and all amps lumped together), requiring only one circuit. But again, multiples are five bucks of parts. max.

 

Here is a Time Constant calculator for figuring out resistors and caps on a timed turn on delay.

http://www.daycounter.com/Calculators/Capacitor-Energy-Time-Constant-Calculator.phtml


A TIP102 would work for use without a Relay. Just remember to use a heatsink.



Turn off delay is a little more complex. The best I ever found is to use an SCR, cap, Darlington and some resistors.

Remember to always use a Diode across all relays to prevent the contacts from burning.

I'll post the circuits I use when I find them.

 

Remember to always use a Diode across all relays to prevent the contacts from burning.

Prevent the contacts from burning? Please explain.

Lifes experience has taught me placing a diode across the coil clamped the huge inductive voltage spike that occurs to coil field collapse once current to the coil is abruptly removed. Prevents you from frying the solid state device that switches the coil on and off.

Running a relay without a diode is actually better for the contacts than running with one. The field collapes faster and the contacts pull away from each other cleaner. Adding a diode prolongs field collapse and allows the contacts to chatter a little more prior to disengaging.

However, if you're only pulling a few hundred millamps through the contacts (remote turn on loads are very low) contact wear may be a non-issue. If anything I'd be concerned more about if you are pulling enough current through the contacts to keep them oxide free.

Just my $0.02

Ge0

 

question:

why should I make these more and more complex turn off delay circuits if the one in post #1 works?

 

the first post doesn't have a well defined turn on delay. also, a smaller transistor can be used in the common emitter configurations I have listed. The common collector setup will discharge the cap through the base of the transistor and the reflected load. this provides relatively poor tolerance for the delay as the delay is based on the current gain of the part (which changes over temp and production by a large amount). further, the turn off switching of the transistor will fall slowly from 12V to 0V. in the common emitter configs, there will be a delay after which a fast transition from 12V to 0V will occur. This reduces the power dissipation of the part as well. the common emitter also has better low-voltage characteristics. it provides within 0.25V of the supply voltage to the coil. the circuit in post 1 provides within 1.5V of the supply voltage to the coil.

In industry, you will see the common emitter config used -- better control, better switched edge, lower losses, lower drop out.

 

and will the regular audio hobbyist notice any of these improvements?

 

if they want a turn on delay or no turn off delay, yes.

 

I'm a newbie and I'm going to try to resurrect this thread, first by asking a few questions?

1. How important is the thumpy thing?
2. Is it true that no one seems to know how to fix it?
3. Is there a device that works?
4. No one seems to understand the problem?
5. No one seems to understand the automotive environment.

I'll attack (4) for a bit:

Problem: Slow turn-on and fast turn-off required for anti-thump

Remote Lead: Some remote leads are actually regulated outputs for antennae preamps. Very tough to use as a remote line because it tends to turn off slowly. Most are relay based. Some may not have the drive (Fan out) to drive all the other devices.

Accessory Power: This one is a big gotcha. It goes through an ON/(OFF)/ON sequrnce when you start the car. The (OFF) is the off that occurs when the starter engages. When the starter engages the accessories turn off. Delay circuit needs an extremely fast reset time.

Timing ckt: Must be at t=0 when entering vehicle. Must reset quickly to t=0 when starter is turning. Once delay has elapsed, the timing circuit must again be ready for the next t=0 event.

Protection: There are +50 and -200 V spikes from the alternator. You need to take steps to protect against that.

Delay time: 0-4 seconds sounds reasonable

Status: Device should have a status LED

Turn-off Thump: Is effectively eliminated with speaker relays. Stubbon cases require muting the input much faster than the speaker relays.

Turn on thump: Fast reset of the timing circuitry is essential otherwise you'll sometimes get thumping because of the pesky ignition switch. Generally delaying the remote lead works. Sometimes a load resistor must be placed on the remote in, so it will decay rapidly.

Thumping is a fault of some component in the loop The ignition sequence being a troublesome input.

Minimum Design: Accept Remote in, Gnd, and Remote Out. Solid state protected output to 1 Amp, short circuit protected. LED indicator, Adjustable delay.

Design Elements Missing: Independent comparator based trigger, Remote Out comes from Battery Terminal, Relay vs Solid state output. Low voltage drop out.

What would an installer/Doityourselfer be willing to pay for such a device (Delay of the remote signal), if one existed? Speaker relays not included, Fan out relays not included, a 3 terminal device without low voltage drop-out.

Comments anyone?

 

Protection: There are +50 and -200 V spikes from the alternator. You need to take steps to protect against that.

Actually automotive conducted transients can get much higher than that. Newer standards state fast transistion rate positive transients can climb as high as +300V and negative transients up to -400V. Mind you, these have a weak energy content, but repeat them a few thousand times a second and this can add up. Slower moving, high energy content, transients can exceed +100V.

This might seem overwhelming at first, but a few precautions on the front end power conditioning circuit can migitate their effects.

Good stuff by the way, keep it up.

The circuit can be as simple as an RC network. Use the time constant of a low pass filter network to set turn on time. Place a diode across the resistor to speed up turn off time. Mind you, timing of this circuit will vary but would be good enough for 90% of the "thump" problems one may encounter.

Ge0

 

Back in the early 90's I designed the delay system with the specifications in the .pdf document. I just typed in this info from page 3. This stuff was done before the Internet and with software packages that are not common today. The board was designed using an Amiga computer.

I had about 200-250 boards made with solder mask but no silk screen. They are not stuffed. I can't even find my test to test the reset circuitry.

The board and components were EXPENSIVE. I haven't figured out the costs today, but there is a BIG problem. The IC I used is discontinued and I only have about 10 of them. The IC's are available, I just don't know how expensive they are and I have to buy a bunch like $200 to $300 worth.

I don't know if it's possible to replicate the functionality with multiple IC's or not, but space constraints would be a problem.

It might be possible to design the board with a new technology. I did solve the reset problem and I think I could do it with a new technology, but again I'm afraid the unit would be expensive.

What should I do?

 

3. A dollar in parts, huh? Let's see the breakdown. Besides there are elements not included that are necessary.

1. Case - about $5.00 in my case, metal lid, 2 extra holes required. Lid can be purchased separately, but for a product would could be purchased drilled and silk-screened. 1 hole in plasitc case for grommet.
2. Transistor mounting hardware. Thermal pad, step collar, screw, nut
3. 3 pieces of wire
4. Grommet for wire
5. 3 DIN Barrier terminals (I left them out too)
6. PC board would be part of this equation too, but $2.50 sounds about right.

Packaging: A box with instructions.

What's this cost of the case/heatsink/wires and the labor to assemble it? In post #1 you have virtually the same costs and clearly it's over $1.00.