SLC DIY Wideband Controller with EGT and more!

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toalan
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Re: SLC DIY Wideband Controller with EGT and more!

Post by toalan »

In the LM317t datasheet, the apps note says that installing a cap on the feedback increases ripple rejection. I have tested in my designs which have to deal with 1khz ripple from switching load @ that freq and it does drop the 1khz ripple I have been seeing on my 5v line drop by 25 percent or so. I do not know where the cap will shift the poles and zeros, the app note does not mention it, i have not observed any instabilities myself.

Yes 5v regulators use feedback or else they will not be able to regulate the load, i mean to say that the lm317 has a physical feedback port for a decoupling capacitor.

I have not tested any of the new generation of regulators, someone mentioned the same to me about the good performance characteristics they have, but I am not quite a believer until I can see it for myself on a scope.

Regards,

Alan To
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Re: SLC DIY Wideband Controller with EGT and more!

Post by MotoFab »

Oh, I see what you mean about having access to the feedback terminal. I get you're a big fan of capacitors. And sure, you gotta use what you're confident in, makes sense.

Rejection is different than reduction of amplification. Reducing amplification of ripple that is already present on the output terminal, by limiting how much of it gets into the feedback terminal, trades that ripple for a lower amplitude level shift. I'm just thinking that if there's already ripple on the output terminal, there may be other perhaps better ways to solve it? I'm not critiquing, I'm just talking.
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Fred
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Re: SLC DIY Wideband Controller with EGT and more!

Post by Fred »

MotoFab wrote:Oh, I see what you mean about having access to the feedback terminal. I get you're a big fan of capacitors. And sure, you gotta use what you're confident in, makes sense.
Do you remember our discussion on the phone when I said that some things you say are difficult to interpret in any way except you trying to be a prick? This is a fine example. Snide. Sideways. Wedge. Patronising. etc.

If your post had purely been the second paragraph, it would have been fine.

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Re: SLC DIY Wideband Controller with EGT and more!

Post by MotoFab »

He says: "i mean to say that the lm317 has a physical feedback port for a decoupling capacitor."
I respond: "Oh, I see what you mean about having access to the feedback terminal."

He says: "I am not quite a believer until I can see it for myself on a scope."
I respond: "You gotta use what you're confident in, makes sense."

He's got 6 capacitors on a linear regulator, I'm sure he knows he's a fan. I would prolly have 1 or 2 in the same situation, or there are the parts that do not use caps. We represent both sides of the capacitor appreciation spectrum.

You say: "some things you say are difficult to interpret in any way except you trying to be a prick?"
I respond: "I get you have difficulty with it Fred."

I'm expressing understanding, you hear patronizing. Ok.
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Re: SLC DIY Wideband Controller with EGT and more!

Post by jbelanger »

Jim,

Do you have a few examples of parts you'd be comfortable using only 1 or 2 caps with? I'd be interested in looking into this.

Jean

EDIT: And sorry if this is off topic.
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Fred
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Re: SLC DIY Wideband Controller with EGT and more!

Post by Fred »

MotoFab wrote:He's got 6 capacitors on a linear regulator, I'm sure he knows he's a fan. I would prolly have 1 or 2 in the same situation, or there are the parts that do not use caps. We represent both sides of the capacitor appreciation spectrum.

You say: "some things you say are difficult to interpret in any way except you trying to be a prick?"
I respond: "I get you have difficulty with it Fred."

I'm expressing understanding, you hear patronizing. Ok.
More of it. Up until now, I've been lenient on you where you've had good material to share. From now on, because I don't have time to be lenient, and because you do not deserve leniency, I will wholesale remove your material if it even looks like it might be snide and underhanded. "I get YOU have difficulty with it Fred" - Jim, with all due respect, and I have a lot for you, technically: Get fcuked! I don't need to tolerate this from you about me, and I certainly will NOT tolerate it when you apply it to other people, especially that I like and respect, such as Alan.
jbelanger wrote:EDIT: And sorry if this is off topic.
You're fine, as always. Relax :-)

Fred.
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jharvey
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Re: SLC DIY Wideband Controller with EGT and more!

Post by jharvey »

That one is close but not the offical. The offical is posted on the SF download page. Yes fusing was handled at the higher level, this is a sub schematic. Glad to hear good things about it. I haven't seen on in person yet, so it's nice to get some real world feed back. Thanks.

How did you find that schematic? My ham call sign is KB1GTT as noted in the above link. Did you happen to come accross it, or did you find it linked some where. I'm just curious.
toalan
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Re: SLC DIY Wideband Controller with EGT and more!

Post by toalan »

I really take no offense over any questions about my design decisions. The point about decoupling the feedback port is perfectly legit, aside from the app note for the lm317 and my experience with the cap being there, I have no defense. At first I was a skeptic because you can not put caps on feedback signals without causing unintended oscillations in most feedback circuits.

He is right on when he says I like caps, I like big caps on inputs with a small decoupling cap, I like big caps on outputs with a small decoupling cap. I have not investigated newer generation regulators because the performance of the lm317t works well for me. I scoped the 5v rails and the linear outputs of competing units and mine were about the same or a bit less in terms of ripple and noise.

I will order some modern voltage regulators and see their performance. If they work better then I will use them for my next design of a high end wideband controller.
toalan
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Re: SLC DIY Wideband Controller with EGT and more!

Post by toalan »

jharvey wrote:
That one is close but not the offical. The offical is posted on the SF download page. Yes fusing was handled at the higher level, this is a sub schematic. Glad to hear good things about it. I haven't seen on in person yet, so it's nice to get some real world feed back. Thanks.

How did you find that schematic? My ham call sign is KB1GTT as noted in the above link. Did you happen to come accross it, or did you find it linked some where. I'm just curious.
I think when anyone looks at the schematic of a power design, they look for protection, if the protection is all there then they will be happy. You got all the protection there, you probably do not need the diode to stop the regulator from being back powered, but seeing it there is reassuring. Actually, you might look over the choice of using a zener for over voltage protection, from what I have seen, they are only good for a few mA in the reverse direction. A TVS diode can do many Amps.

I am into Ham myself, smoked, honey glazed, really any type of Ham, that is how I found your schematic. Actually it was posted somewhere in this forum.
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Re: SLC DIY Wideband Controller with EGT and more!

Post by MotoFab »

toalan wrote:He is right on when he says I like caps, I like big caps on inputs with a small decoupling cap, I like big caps on outputs with a small decoupling cap.
Have you ever tried the solid aluminum organic semiconductor caps? I once tried out some 10uF-100uF samples in a design just to see how they worked. I think they were Panasonic or Vishay OSCONs or OSCAPs or something, but I haven't seen them around and don't know if either mfg still makes them. I've never seen anything like them, very impressive. I mean, if you haven't used them you're in for a real treat. Purposely make a noisy circuit and these things will probably take care of it.

Anyway, the problem was noise from the address controller for a bank of 1Mx1 (bit wide) high speed static rams each with 20 address lines. This was a lot of address lines, very much like the DRAM addressing on a PC. The caps worked amazingly well to 'absorb' the noise, but I didn't use them. Mostly, to me that is, issues don't look like they're caused by not enough of something, they more look like too much of something else. But that's just a raise the bridge or lower the water decision, mostly either one will work.
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