DIYEFI.org Forum

I received the kit from Alan in the mail this morning and it's now shortly after 4am and I'm off to bed with it 99% complete and ready for some testing in the morning.

Read about it here:

http://14point7.com/Widebands/SLC_DIY/SLC_DIY.htm

I can post some pics of it tomorrow, it's a pretty sweet little box! :-)

Fred.

Where are these pictures?

Great use of the smiley! I'll get some pics up as soon as possible :-) Keep bugging me if you're impatient.

Fred.

The link above is broken, try this instead: http://14point7.com/SLC-DIY.php

hmm, I wonder why free-air cal is only 'required half as often'

I'd also like to hear an explanation of what 'programmable switch capacitor' is. While we're at it, why are 2 fuses better than one ?

Thanks kjb :-)

Alan needs to add this to his config, I'll email him.
EssEss, perhaps he's reversing polarity like the LC1 does? I'm not sure why 2 are better than one, but my unit only has one, so the point is moot.

Fred.

EssEss wrote:I'd also like to hear an explanation of what 'programmable switch capacitor' is. While we're at it, why are 2 fuses better than one ?

Heh heh, because if one fuse fails the other one is a backup!

He prolly means switch capacitor filter.

EssEss wrote:I'd also like to hear an explanation of what 'programmable switch capacitor' is.

Sounds like a PSoC to me. That should allow some flexibility in on the fly changes to hardware. Perhaps it's a switch cap filter like the LMF100, who khows.

EssEss wrote:While we're at it, why are 2 fuses better than one ?

I've seen high side and low side fusing, but that's mostly for higher voltage and multi voltage devices. I feel the low side fuse is junk, but it's required by some codes.

The dual fuse thing is probably a thermal overload "PTC" like you sometimes put on speakers like tweeters to prevent damage. I did solder in something that I wouldn't call a fuse, but that could be one of those. It's not unreasonable to call it a fuse, though. More of a solid state circuit breaker :-)

Fred.

EssEss wrote:hmm, I wonder why free-air cal is only 'required half as often'

I'd also like to hear an explanation of what 'programmable switch capacitor' is. While we're at it, why are 2 fuses better than one ?

That stuff is not applied to SLC DIY, that is SLC Pure Plus.

Half as often primarily because innovate requires both a heater calibration and a pump cell calibration, both are done at the same time when you trigger calibration on the innovate stuff so it looks like just one calibration. Innovate does not measure the nermest temperature directly but measure the pump cell temperature and use a scaling factor as a proxy to the nermest temperature, the heater calibration is used to find the scaling factor. Pump cell calibration is the only calibration I do as my system measures nermest resistance directly. Because only 1 factor changes instead of the 2 for innovate, I am comfortable saying that you only need to calibrate half as often. With that said our system does not need free air calibration in the first place to hit 0.01 lambda accuracy, so users can run without free air calibration and still be very accurate.

Programmable switch capacitors are built into the cypress PSOC uCs. Basically you can swtich capacitors on/off in different configurations to emulate the V I characteristics of a real resistor. The configuration and the switching is programmable. Each programmable switch capacitor block is composed of switch capacitors and an OP amp. Pretty much, once you have an op amp, resistors and capacitors, you can make a wide variety of analog peripherials. If you crack open almost any wideband you will see that they use an external DAC, external instrumentation amplifier, and external filters, all that and more in my design is done onboard the PSOC using switch capacitor blocks, saves money, saves space, and the programmable flexibility gives my stuff an accuracy and performance advantage.

The max the current for the electronics is 100ma, the max for the sensor is 3A. I can use a single 3A fuse for both the electronics and sensor but that would only protect the electronics such that they do not catch on fire. I can not use a 100ma for both the electronics and sensor as it will blow left right and center. I can use just a 100ma for the electronics, but the sensor will get destroyed if reverse load dump happens. Alternatively I can not use fuses at all and protect my ass by offering a short warranty like other units do.

The fuses I use are physical fuses that blow, I used to use PTC resetable stuff, but I am not comfortable using them in an automotive setting were cabin temps and direct sunlight will cause temperature issues for the PTC fuse. For SLC Pure Plus I provide an additional set of backup fuses in each order.