Isolating U5 (Voltage Regulator) from the heat sink

Ask questions about DIY board assembly issues, fault finding and testing. (Covers all Megasquirt versions and board.)

Moderators: jsmcortina, muythaibxr

Isolating U5 (Voltage Regulator) from the heat sink

Postby jsdevel » Fri Sep 22, 2017 5:11 pm

For boards v3.0 and v3.57, is it possible to isolate the U5 voltage regulator from the heat sink with thermal grease on both sides of a mica insulator? Are there any circuits that depend on sharing a connection with it's heat sink?
jsdevel
Experienced MS/Extra'er
 
Posts: 294
Joined: Mon May 23, 2016 3:41 pm
Location: Phoenix, AZ

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby billr » Fri Sep 22, 2017 7:20 pm

I think the circuit could work with the tab insulated from ground, as long as the center pin is still connected to ground as intended. But, I gotta ask... why??? All you would achieve is more heating of the U5 package, the tab would still be connected to the heat-sink via that center pin. What are you trying to accomplish here?
billr
Super MS/Extra'er
 
Posts: 5011
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby jsdevel » Fri Sep 22, 2017 7:39 pm

Basically just trying to reduce noise. I'm having horrible problems with resets.

Sent from my Nexus 6P using Tapatalk
jsdevel
Experienced MS/Extra'er
 
Posts: 294
Joined: Mon May 23, 2016 3:41 pm
Location: Phoenix, AZ

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby billr » Fri Sep 22, 2017 7:52 pm

I see no way that could reduce a noise problem; increase it if anything. Do you have another thread going on the noise problem?
billr
Super MS/Extra'er
 
Posts: 5011
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby jsdevel » Fri Sep 22, 2017 8:04 pm

billr wrote:I see no way that could reduce a noise problem; increase it if anything...


Isolating it does seem to have made the issue worse! Perhaps grounding my case at this point would help?

billr wrote:Do you have another thread going on the noise problem?


I have a few. Trying to keep them separated to stay focused on different theories:

jsdevel
Experienced MS/Extra'er
 
Posts: 294
Joined: Mon May 23, 2016 3:41 pm
Location: Phoenix, AZ

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby DaveEFI » Sat Sep 23, 2017 1:13 am

jsdevel wrote:
billr wrote:I see no way that could reduce a noise problem; increase it if anything...


Isolating it does seem to have made the issue worse! Perhaps grounding my case at this point would help?

billr wrote:Do you have another thread going on the noise problem?


I have a few. Trying to keep them separated to stay focused on different theories:



I never ground the case. If fitted direct to the car body, I insulate the mountings. Grounding is best only be done at one point.
Rover SD1 3.5 EFI
MS2 V3
EDIS
Tech Edge O2
London UK.
DaveEFI
Super MS/Extra'er
 
Posts: 2775
Joined: Sun Apr 15, 2012 12:55 am

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby jsdevel » Mon Sep 25, 2017 11:11 pm

Upgraded all my grounds, now grounding everything at the battery. Hasn't helped at all.

Here's my new theory: Invalid Closed Loop Idle Settings
jsdevel
Experienced MS/Extra'er
 
Posts: 294
Joined: Mon May 23, 2016 3:41 pm
Location: Phoenix, AZ

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby billr » Tue Sep 26, 2017 9:09 am

Well, you have a whole lot of threads going on this same basic problem; it's kind of hard to keep track of what has been discussed.

However, in one thread it was mentioned that the 5V may be being pulled low by something. That may be happening too fast for it to show regularly in the logs. It might be time to consider using a scope on that 5V. If this isn't something that can be reliably repeated, then maybe somebody can suggest a simple DIY circuit that can monitor that 5V and "latch" for later reading if the 5V goes below 8V or so.
billr
Super MS/Extra'er
 
Posts: 5011
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby jsdevel » Thu Sep 28, 2017 12:55 am

billr wrote:Well, you have a whole lot of threads going on this same basic problem; it's kind of hard to keep track of what has been discussed.


I know :cry: I'm truly sorry about that. It's been a crazy 9 months moving, having my wife give me rides to work, and frantically banging my head against the bricks labeled hard knocks, but I have hope! Once I have it running (which I will!), I plan on tying all this together 8)

billr wrote:However, in one thread it was mentioned that the 5V may be being pulled low by something. That may be happening too fast for it to show regularly in the logs. It might be time to consider using a scope on that 5V. If this isn't something that can be reliably repeated, then maybe somebody can suggest a simple DIY circuit that can monitor that 5V and "latch" for later reading if the 5V goes below 8V or so.


I pulled U5 and tested it, had virtually OL across all pins. I had some new ones from digikey to compare my readings against. I've ruled that out.

I discovered that my DSM CAS was defective. I ordered a new one and have it coming tomorrow. I'll be reporting back here once I have it installed. Fingers crossed!
jsdevel
Experienced MS/Extra'er
 
Posts: 294
Joined: Mon May 23, 2016 3:41 pm
Location: Phoenix, AZ

Re: Isolating U5 (Voltage Regulator) from the heat sink

Postby billr » Thu Sep 28, 2017 10:30 am

"... if the 5V goes below 8V or so."

Did you folks note my mistake there? I should have said "if the 5V goes below 4.8V or so". No, it wasn't a simple typo; I was talking about the 5V but thinking of a low limit for the raw 12V.
billr
Super MS/Extra'er
 
Posts: 5011
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA


Return to Board assembly and testing

Who is online

Users browsing this forum: Bing [Bot] and 1 guest