#### gte

Joined Sep 18, 2009
353
I don't think it would take more than 2 hours to design, but $50 was just an example? But if it did, I would of course be willing to pay what is fair? My circuit is very simple I think? But I wouldn't know, cause I don't know how to build it . If you can point me to someone willing to do this, I can give them the specifics and then can give me an estimate I guess? Such a site would not last long. How much do you suppose a person's time is worth.$50.00 might get you 1-2 hours from an out of work engineer and slightly more hours for a technician. Is it your contention that the task you are asking for should actually take less time than that so there is room for some profit?

#### bertus

Joined Apr 5, 2008
19,939
Hello,

What do you want to be build?
What is simple, but you can not build it?

Greetings,
Bertus

#### ELECTRONERD

Joined May 26, 2009
1,146
You can pay a board layout manufacture to build a board design you submitted to them and then they'll send you the board in the mail. I think PCB Electronics or something had a deal where you could get 3 boards for $50. You could simply solder in the components and you'd be done. #### Papabravo Joined Feb 24, 2006 12,301 I don't think it would take more than 2 hours to design, but$50 was just an example? But if it did, I would of course be willing to pay what is fair?

My circuit is very simple I think? But I wouldn't know, cause I don't know how to build it . If you can point me to someone willing to do this, I can give them the specifics and then can give me an estimate I guess?
Well that is the crux of the matter. Regardless of the simplicity of the circuit I think the amount of time and effort required to meet your requirement is off by at least one and maybe two orders of magnitude. At $500-$5000 in cost it may be worth your while to reconsider the worth of your own time and effort. Many people on this board have resolved that dilema in favor of expending their own effort to learn and understand instead of parting with their hard earned resources.

The short answer to your original question is: unlikely you can find anybody to do it for $50. Chances are improved marginally at$500. Chances become significant at $5000, and a virtual certainty at$50,000.

Anyway if you can find someone you trust to generate a quote then by all means go for it.

FYI
If you have a design that you wish to make and sell, for simple boards containing a processor, some I/O, and some connectors the following budget is not atypical

PCB Layout: $1200-$1500
PCB Fab: in 100 Qty $450 in tooling and$10.00/board
PCB Assembly: $700 in tooling and$6.00/board

You can get quick turn PC boards at higher unit costs like $60-$75 ea for 2 or 3 boards

Last edited:

#### gte

Joined Sep 18, 2009
353
@Electronerd - I guess I first need a .sch or .pcb design file to send to them

@Bertus ( a video of the values needed is at the bottom of this post )

I need an electronic circuit that can mimic these voltage readings

Step 1: 1.614 vdc before the pump runs
Step 2: 1.833 vdc while the pump runs
Step 3: 2.041 vdc as the pump turns off
Step 4: 1.574 vdc after the pump turns off

The circuit will when the pump is on and off via a ground signal that will be the trigger and is already part of the car.

I can build the part of the circuit with the voltage converter and specific voltage outputs, and a relay (probably crude) to control the transition between Step 1 and Step 2.

What I don't know what to do:

How to get the voltage to spike up to 2.041 when the relay is released?

How to get the voltage to settle back down at 1.574?

How to not let the voltage that is coming out of the sensor output wire/ecu signal input wire, to skew the voltage value that is coming out of my circuit? I tried a zener diode, and I had to compensate an additional .4 volts or something? I don't know why that was either?

Hello,

What do you want to be build?
What is simple, but you can not build it?

Greetings,
Bertus

#### gte

Joined Sep 18, 2009
353
Hi,

I'm ok with building this on a generic board like the ones you can buy at Radio Shack or an electronic supply store. I'd love to learn about micro controllers also, is that covered in the "All about circuits" e book? I didn't see it in the table of contents, and I'm only on chapter 2 at the moment.

Which micro controller would you suggest, and which programming language does it use? I'm hoping my novice programming experience can port over into micro controller programming?

There is no "simple" circuit that can do this very cheaply. You are propably looking at a either a state machine (which involves a bit of boolean calculations and a bunch of integrated circuits)

Or a microcontroller controlled circuit (propably cheaper then the state machine) but requires programming.

And also you need a power supply capable of supplying multiple voltages or somehow very easily and dynamicly re-adjusted for other voltage levels.

I dont think either of these circuits are under 50\$, and the work alone is definitely worth alot more.

#### gte

Joined Sep 18, 2009
353
It appears that the system has a check valve in it, that only allows the pressurized air to flow one way, and when the valve seals, the other side of the diaphragm can then oscillate it and vary the pressure in the sealed chamber (sort of how a mechanical fuel pressure gauge works, with an in cabin isolator), which explains why the voltage readings drop lower than when the key is at the on position/vehicle off, after the pump turns off. The exhaust creates a venturi effect and oscillates the diaphragm, which in turn creates a low pressure situation.

Here is a log of the car running at idle for a few seconds. When it cools down, I will log the entire time the pump is one and when it spikes up, then settles down.

It is timed, and it seems to be dependent on coolant temp, the good news is that none of this matters because the ecu controls the timer and a solenoid, which can be taken advantage of to be the input that controls timing on this device.

Rich (BB code):
Parallax USB Oscilloscope
Sample Rate: 250S/s
9/21/2009 7:00:24 PM

Time us, CH1 V, CH2 V
4000,1.56,0.00
8000,1.48,0.00
12000,1.48,0.00
16000,1.56,0.00
20000,1.56,0.00
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1688000,1.48,0.00
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1700000,1.48,0.00
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1708000,1.48,0.00

#### gte

Joined Sep 18, 2009
353
Here is a description of the circuit from the service manual, I'm getting code 2441 with my current circuit.

If I'm reading it correctly, it continually monitors this circuit and makes sure that it gives a pressure reading when the air pump is on, and a vacuum reading when the air pump is off, and the vacuum signal should oscillate with the pulses of the engine?

http://freepdfhosting.com/ee3362e89e.pdf

Last edited:

#### bertus

Joined Apr 5, 2008
19,939
Hello,

The PDF does not contain the information.
It contains : "factuur voor comodossl certificaten"

Greetings,
Bertus

PS de factuur is in nederlands gericht aan iemand in delft