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Old 02-03-2010, 04:44 PM   #121
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Where did you get them? Farnell doesn't have them, and if they don't, I don't know who does.

Jim
There's this small electronics shop half an hour from me where I can get them. They are special order, so I usually have to wait a week or 2 before they have them. Last time I had to order them by 5. Still no big deal as they're not expensive.
Some items can't be ordered though, like the IRLZ44 for EBC for instance. Had to get that from Glenn's Garage.
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Old 02-03-2010, 05:31 PM   #122
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Ok. I'm going to try with a fully digital circuit, as the parts required there are much simpler to find.

Jim
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Old 02-03-2010, 09:53 PM   #123
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I had minimal luck at Radioshack. Or should I call them Cellphone Shack. They had the transistors, but no 1% tolerance resistors. Napa Auto parts next door was even more useless than the Radio Shack staff. Oh well, mail order for me.
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Old 02-03-2010, 09:59 PM   #124
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I used 5% tolerance resistors. They come in a multi-pack. Measure across them with a DMM and use the closest ones. They're typically dead on, or nearly dead on, anyway.
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Old 02-03-2010, 10:02 PM   #125
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Originally Posted by Reverant View Post
Ok. I'm going to try with a fully digital circuit, as the parts required there are much simpler to find.

Jim
What is involved in going digital? Is it more expensive than a bag full of solid state parts?
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Old 02-04-2010, 02:26 AM   #126
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What is involved in going digital? Is it more expensive than a bag full of solid state parts?
Probably more expensive, but not by much. I will use the same circuit for a bunch of other stuff (like proper A/C control, battery & MIL light, 2nd fan control, etc) so the cost is not really tied to the alt control alone.

Jim
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Old 02-05-2010, 10:42 AM   #127
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If you guys have trouble finding components, try Mouser.com. Very wide selection and no mins if stocked. They are global, and usually at your door within 3 days.
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Old 02-05-2010, 01:46 PM   #128
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Have a look where we're all from.
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Old 02-05-2010, 03:27 PM   #129
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Mouser has sales in Europe and Asia and ships worldwide, usually in 3 days. I hear of people having trouble sourcing electronic components, so i thought I would help. They have always had what I need.
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Old 02-06-2010, 12:01 AM   #130
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If you guys have trouble finding components, try Mouser.com. Very wide selection and no mins if stocked. They are global, and usually at your door within 3 days.
Just placed order. $2.27 for everything. Oh wow, going to return this $12 half a bag of Radio shack parts.
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Old 02-06-2010, 07:50 AM   #131
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Mouser, and in fact, no one else online, lists the TL431/CYL. Sure, there are other variations listed, but which one is right for this application?

Jim
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Old 02-06-2010, 08:22 AM   #132
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Jim, if you want me to mail you a letter with a TL431 in it, gimme a shout. I'm in the neighbourhood of that shop next week so I can stop by to get you one. Last time I ordered they told me they would stock a couple.
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Old 02-06-2010, 10:33 AM   #133
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Thanks Frank!

I'm going to try a custom circuit tomorrow on a friend's car, and if it doesn't work then I'll let you know. Thanks again!

Jim
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Old 02-08-2010, 02:16 AM   #134
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I'd only put one there if you're having problems, and it wouldn't need to be as big.

On the 12v, we have a 3300uf cap on the MSPNPs, which is really bigger than needed. Without the cap the stock electrical system (12v) gets somewhat noisy when the engine is under load. With about half that value smooths out the 12v pretty nicely, now having a nice nearly flat 12v (or 13.2 or whatever, bottom line is it stopped it from looking like a sine wave anymore) under load. The 3300uf made it pretty much perfectly flat, just a slight improvement over the smaller value. The cap was cheap, so I used the bigger one, done deal.

I discovered this a couple years ago when troublehooting the occasional misfire issue we used to see. Turns out I solved that with a much smaller cap on the 2nd input to filter the 2nd trigger, and noise on that signal had been the root cause of that. This cap on the 12v really is not required at all, but doesn't hurt, may help in some cases, so we left it in. BTW, before someone asks, there is already filtering on the DIYPNP's 2nd trigger, this little cap shouldn't be needed.
I got my car running and have been road tunning it for a couple of days. My big issue now is the occasional hiccup accompanied by a sudden loss of tach signal. Looking at the log it seems like MS2 is loosing sync for an instant and then catches back on. I want to try Jerry's capacitor on the 2nd tach signal line. Jerry, what size capacitor did you use?

Thanks.
-Raj
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Old 02-09-2010, 01:12 PM   #135
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It's a 0.1 uF - and too large for MS2.
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Old 02-09-2010, 01:57 PM   #136
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We put the alternator circuit together a few weeks ago and I thought it was working fine. In Tunerstuidio I read 15v all the time the car is running, isn't that a little high?
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Old 02-09-2010, 02:32 PM   #137
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That's a little high, but probably not dangerously so--as long as you're not going over 15v. You might go through headlight bulbs a little quicker.
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Old 02-09-2010, 02:47 PM   #138
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You really should check the voltage at the battery using a DVM.
When my DVM said 12V battery voltage, MegaTune said 11.6V. Battery voltage is determined with a resistor voltage divider to bring the 12 volts down to under 5V for the MCU to convert. R3 (50K) and R6 (10K) on the Megasquirt PCB form this voltage divider. These are both 5% tolerance resistors and in my case, the ratio was 5.22 instead of 5, causing the difference between actual and MS values for battery voltage. It's best to use 1% resistors for this. It's important to have a correct reading because the MS changes certain values (injector opening time, dwell etc) depending on the input voltage.

If you find that everything is correct and you really measure 15V at the battery check if you used 1% resistors in the alternator circuit. The setpoint is determined with the formula: 2.495V*(1+ R4/R11), so it's important to use 1% resistors for R4 and R11. I used a 5% for R11 and found my setpoint to be 15.1V!
If you used 1%, you might want to replace the 48K7 resistor with a lower value like 47K5 or 46K4. Make sure your setpoint is about 14.4V. In your case, you'd have to use the 46K4 resistor to get 14.4V if you now have 15V.
Although 15V is still within spec, I don't feel comfortable with it. Your bulbs as well as your battery will live longer at 14.4V
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Old 02-09-2010, 03:29 PM   #139
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Quote:
Originally Posted by Matt Cramer View Post
It's a 0.1 uF - and too large for MS2.

2nded I fitted the cap and it ran fine apart from a complete loss of sync around 5k. remove the cap al all was golden.

If you were to run a cap though, what would you recommend?
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Old 02-10-2010, 04:42 PM   #140
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Quote:
Originally Posted by f_devocht View Post
You really should check the voltage at the battery using a DVM.
When my DVM said 12V battery voltage, MegaTune said 11.6V. Battery voltage is determined with a resistor voltage divider to bring the 12 volts down to under 5V for the MCU to convert. R3 (50K) and R6 (10K) on the Megasquirt PCB form this voltage divider. These are both 5% tolerance resistors and in my case, the ratio was 5.22 instead of 5, causing the difference between actual and MS values for battery voltage. It's best to use 1% resistors for this. It's important to have a correct reading because the MS changes certain values (injector opening time, dwell etc) depending on the input voltage.

If you find that everything is correct and you really measure 15V at the battery check if you used 1% resistors in the alternator circuit. The setpoint is determined with the formula: 2.495V*(1+ R4/R11), so it's important to use 1% resistors for R4 and R11. I used a 5% for R11 and found my setpoint to be 15.1V!
If you used 1%, you might want to replace the 48K7 resistor with a lower value like 47K5 or 46K4. Make sure your setpoint is about 14.4V. In your case, you'd have to use the 46K4 resistor to get 14.4V if you now have 15V.
Although 15V is still within spec, I don't feel comfortable with it. Your bulbs as well as your battery will live longer at 14.4V

We did use a 1% resistor but we did not test it, I'll look at it again tonight. Thanks for your help.
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