Power and Heat considerations (enclosures, etc)

[brucepick]

I'm interested in using an external regulator and the capacitor(s). I could put them under the dash or in the engine bay.

dcb,

Can you give some details on the capacitor(s)? I'm guessing they are wired across the + and ground, both before and after the regulator?? What rating caps?

And how to read the three "legs" on the regulator? I've seen pics of them but don't see markings I understand.

I put the suggested 8 ohm resistor in line with the 12V power. It does help the Guino stay reasonably cool.

However, after serious EOC, I've seen the Guino reset itself. (Gallons used etc. go to zero, and the Guino goes to the home screen which I think is "Custom".) I'm theorizing that with battery power dipping into the 10V range or lower, the 8 ohm resistor is too much, and it doesn't get the power it needs.

Thanks!

[brucepick]

If the Guino uses 20 ma with the lcd off and I put a 3-pin VR in the power line, will the VR now consume additional milliamps when the lcd is off? How much?

[dcb]

I'm a little confused about the setup. was still thinking about the resets. Do you use the starter? That can make a large voltage drop as well.

you are using an external 8v regulator and an 8 ohm resistor? That might be overkill, dunno.

but just an 8v regulator should not add any noticable milliamp drain.


FYI I am currently using a 470uf cap and two .1uf caps with the regulator, and low power backlight, which is not fed through the regulator (schematic in post 8), but rather is fed 12v through a resistor and has the bottom leg pwm'd. So it is a sort of switching power supply just for the lcd backlight.

[brucepick]

Voltage regulator not yet bought. Probably today. Need the caps too but which ones and where do they go? Polar or non polar??

I plan to ditch the resistor when putting in the regulator. I'm not up to wiring inside the guino assembly. It will all be external to it.

Usually when doing eoc I bump start it but i will use the starter after sitting at a light. Definitely there's a voltage drop with starter use and that could be when it resets due to the 8 ohm resistor.

Sorry I don't follow your last paragraph about the latest guino components. I can solder OK. The 8 ohm resistor is in a 4x2x2 project case with a major vent hole so I think I'll put the VR and heat sink in there instead of the resistor. Or maybe screw to the firewall for a heat sink.

Thx.

[dcb]

You have a prebuilt, no? do you know what version is it? 1.1 or 1.3?

[brucepick]

Prebuilt from you. Sorry don't know the version. I remember I sent it back once and you replaced either the LCD or the whole thing. You recall?

[dcb]

ok, probably 1.1. lemme see if I can whip up a diagram.

[brucepick]

OK. I'm headed out to get the 8V regulator at an electronics store here and other errands. I'll check later for any caps info.

[dcb]

I *think* this should do it using radioshack parts. The cap is kinda expensive, I just grabbed the biggest one they had to help address the resets.

You probably won't need an extra regulator with this, as you have a voltage drop in the diode and the 8 ohm resistor.

So when you start the car, the idea is that this will help maintain a higher voltage for the guino. Dunno if it will help though. If you can salvage a 25v (or higher) large cap that would be cheapest.

4700µF 35V 20% Axial-Lead Electrolytic Capacitor - RadioShack.com
4700uf axial cap

1N4001 Micro 1A Diodes - RadioShack.com
1n4001 diode

8-Ohm Non-Inductive Resistor - RadioShack.com
8 ohm resistor

[brucepick]

OK - I could add this to my existing setup.

I was all set to ditch the resistor and put in the 8V regulator.

You think the big cap + diode + resistor is better than using the 8V regulator, without the resistor? Is there a down side to the regulator??? I mean a negative aspect. I mean, this d**n English language is a minefield for double meanings. Is the VReg a worse plan?