Widebands That You Would or Wouldn't Buy

[HelmutVonAutobahn]

I don't know. I have not looked at the GEN1 PCBs.

But, the GEN2/GEN3 PCBs lack any kind of reverse voltage protection. The power lines connect directly to a 330uf aluminum ( polarized ) cap. No blocking diode. No PTC fuse, etc.

Its a pretty simple design. Most of the work is done by the PIC18F2410.
The rest of the circuit is 3 LM2902 amps, a couple of LM1117 regulators ( 5.0v and 3.3v )
A 452A MOSFET for the heater. A sprinkling of 3904s 3906s and BAS16s
The rest is all Rs and Cs

I like that they went with a P-channel FET for the heater drive.

[toalan]

Can you find a DAC on the board? If so what is the part #?

[HelmutVonAutobahn]

There is no DAC. Just PWM from the PIC18F2410 into an RC LPF, buffered by on of the LM2902 amps.
Same basic implementation as the Innovate LC-2

This is a very simple board. What I listed ( plus the crystal ) is literally ALL of the components.

[HelmutVonAutobahn]

But, if you want a mystery, like the Innovate LC-2's switcher regulator...

It LOOKS like the CPU is powered by the output of one of the amps.

[toalan]

The Gen 1 that I have:
-Electrolytic caps, no reverse diode protection, no fuse, no over voltage protection.
-Used a DAC, probably for the pump cell, might have been a 2 channel DAC for pump cell and linear output, it was a commercial grade DAC
-It had dual voltage regulators, I think 5v (maybe 3.3v) and 9v, the 9v was for providing greater current drive to the pump cell for faster response.
-The heater PWM frequency was insanely high like 200khz, which generated alot of heat, I thought was a timebomb since the DAC was only commercial grade and the electrolytics would constantly heat cycle in winter.

Seems like 2013 is the year of the PWM DAC.

[HelmutVonAutobahn]

The 200kHz might explain the huge 1210 sized 1k gate pull-up resistor on the MOSFET. That's 200mw @ 14v

With no high-side driver ( just a 3904 ), they probably need it to keep the FET out of linear range ( heat death ) at hi freq,
due to gate capacitance.

As for driving the pump, the max limit is 6ma. So, the LM2902 output is plenty. They can't be looking for TOO much speed. Their PWM R/C filter is -3dB @ 13Hz
12k/1uf So, their best possible t90 is around 175ms. That's just the DAC's latency. Even if their sensor circuit is 2X faster than the CJ1xx , they would still come in at about 300ms t90.

They claim to be using a PID to control the pump current. But, I guess that is a PWM DAC, as well, now. The Bosch CJxx chips just run the feedback through a LPF which is over-damped.

I am not a fan of PWM DACs.

[HelmutVonAutobahn]

Your mission, should you decide to accept it, is to identify which is the GEN2 and which is the GEN3 PCB.

The housings are also identical. No indication of which generation product it is.
The packaging and instructions are also identical. Except for a single place-card sized sheet of paper marked "SM-AFR Generation 3 Supplement"

The "Health" feature just seems to be a measurement of how far off of 20.9% oxygen ( 2.55ma indicated )the device is when told it is in free air. i.e. I was able to control it by putting a resistance sub box in place of the sensor trim resistor.

The sensor reaction time seems to be the number of milliseconds taken between the last time the sensor crossed lambda 1.0 and free air. ( or something close to it ). It was hard to get an exact correlation on the scope because the R/C filter on the PWM DAC is only 13Hz t63. That actually makes sense. as the serial data rate is 10Hz. I assume the device stores the last transition time, internally. Then, reports it, when queried.

I hope AEM is monitoring this thread. The bar is set kinda low, guys.

[Fred]

Sorry for a worthless post here, but thank you very much for contributing all of this information! I'm following avidly and enjoying every post. As for AEM, I'd rather support Alan, however his stuff likely already smashes the competition in every way.

[HelmutVonAutobahn]

Happy to be so entertaining

I mentioned AEM because they would be "next" with the new generation of widebands.



I need to get one of Alan's toys to play with.
I looked at his website. But, I didn't see any specs.

[Fred]

His website just got MAJORLY upgraded. I'm unsure if he has added hard-core tech specs, or not. They're probably not conducive to normal marketing, though. Maybe a "details" tab thing or similar?