Separate Brake Light From Turn Signal

[ThomsCircuit]

I'm glad I got the pot's wired correctly.
I was able to increase the trace that requires 3 amps to 70

 

[eTech]

Hope you like Italian.

As long as she's beautiful.

SCHEMATIC. Detail Mosfet IRF5305

The mosfet drain and source are transposed. The drain should connect to the LED.

 

[eTech]

I'm glad I got the pot's wired correctly.
I was able to increase the trace that requires 3 amps to 70
View attachment 145999

The mosfet gate can be a narrow trace. The mosfet drain and source need to be a fat trace.

The other side of D8 needs to be fat to the V+ pin.

 

[ThomsCircuit]

The mosfet gate can be a narrow trace. The mosfet drain and source need to be a fat trace.

The other side of D8 needs to be fat to the V+ pin.

OK got it. I did think that was not right but the images were throwing me off.
So what I did now was
gate: trace is narrow (30)
Source: I moved that trace to the bottom layer and added a rectangular pour
Drain: Left that trace on the top layer and added a custom shape pour.
I also added a small rectangular pour on the other side of D8 where it connects to the positive input also on the bottom layer.

 

[ThomsCircuit]

 

[eTech]

OK got it. I did think that was not right but the images were throwing me off.
So what I did now was
gate: trace is narrow (30)
Source: I moved that trace to the bottom layer and added a rectangular pour
Drain: Left that trace on the top layer and added a custom shape pour.
I also added a small rectangular pour on the other side of D8 where it connects to the positive input also on the bottom layer.
View attachment 146000

1. I think the fat Source and Drain traces without the pours will be fine.

2. VDD pour: make the thermal pad(s) spokes fatter without violating rules.
I think you can do this in DSPCB by pointing at each spoke and setting the width.

3. Minor details (observations):
a. why the "+" on diodes D9,D10 silkscreen?
The stripe indicates polarity, so the "+" really isn't needed. In addition to the stripe, a square
pad can be used to indicate the "cathode".
b. BJT transistors usually have a square pad to indicate the "emitter".
c. Polarized capacitors usually have a square pad to indicate the "+" pin.
d. IC's usually have a square pad to indicate the pin 1.
e. Might change "OUTPUT" to "+OUT" to indicate it is a positive output when active.
f. The square pads mentioned above help when troubleshooting from the bottom side of PCB.

Section 3 is a list of my observations and don't necessarily require changes to the PCB.

 

[ThomsCircuit]

1. I think the fat Source and Drain traces without the pours will be fine.

2. VDD pour: make the thermal pad(s) spokes fatter without violating rules.
I think you can do this in DSPCB by pointing at each spoke and setting the width.

Made the changes. Moved the mosfet so it can be laid down with heat sink facing up. Larger spokes on the small VDD pour and removed the other pours. Altered components so they can be identified from the bottom.

 

[crutschow]

As you still considering also building the circuit I proposed, or are you just going with this one?

 

[ThomsCircuit]

As you still considering also building the circuit I proposed, or are you just going with this one?

I am making both. Its only a few dollars and you were so kind to assist me. I will have a bit of down time for about a month as I am having bi-lateral knee replacement in a few days so while I cannot install the new lights on my trailer I can sit and solder. I have located all the components and am just fine tuning the layout. On another note I have learned a great deal as I can make decisions on alternate parts, make & read schematics, layout components for PCB fabrication and understand suggestions from members and make corrections.
For your design, I wanted to test the surface mount circuit you designed so I'm also getting for breadboard mounts to adapt the SMD IC's. By the way did you get yourself a plate of meatballs?

 

[eTech]

Made the changes. Moved the mosfet so it can be laid down with heat sink facing up. Larger spokes on the small VDD pour and removed the other pours. Altered components so they can be identified from the bottom.
View attachment 146023

Looks OK.

Don't change anything, but it would make more sense if the mosfet was moved next to the OUT+ terminal (shorter high current S/D traces, long gate trace ok). The shorter the trace, the less resistance, the more current carrying capacity. Maybe pick that up after prototyping.

 

[crutschow]

By the way did you get yourself a plate of meatballs?

No, but I had a Subway meatball sub a few days ago.

 

[ThomsCircuit]

Don't change anything, but it would make more sense if the mosfet was moved next to the OUT+ terminal

I took care of it. Relocated the Out+.
Thank you.

 

[ThomsCircuit]

These are ground vias. A ground bottom layer copper pour added the spokes. I don't need these do I? Design Spark allows me to change their isolation so they wont have any. Should I?

 

[eTech]

These are ground vias. A ground bottom layer copper pour added the spokes. I don't need these do I? Design Spark allows me to change their isolation so they wont have any. Should I?

Thermal pads are only needed for pins that connect to a pour. Thermal pads are intended to act as a "thermal isolators" so that the pin can be heated enough to be soldered. If there is no pin, and a thru hole connection is needed, then the hole should be an ordinary via.

 

[ThomsCircuit]

If there is no pin, and a thru hole connection is needed, then the hole should be an ordinary via.

Thought so. Thanks.
I am going to use a 555 to simulate a turn signal and configure it to match the 80 cycles of my Tundra.. I'll feed this to the circuit so I can adjust the pot from my workbench.

 

[crutschow]

Thermal pads are intended to act as a "thermal conductor" so that the pin can be heated enough to be soldered.

Actually, they are to provide some thermal isolation, so the ground copper ground plane doesn't conduct so much heat away, that it's hard to solder the pin.

 

[eTech]

Actually, they are to provide some thermal isolation, so the ground copper ground plane doesn't conduct so much heat away, that it's hard to solder the pin.

Yes. Agreed. That's what I meant. It's actually a "thermal isolator".
It helps prevents the pour from acting like a heat sink. I've corrected what I wrote in #114.

 

[ThomsCircuit]

I used a site to help me get a equal on/off time in a period of .8 seconds. Similar to my trucks cycle. I can replace R2 (24k) with a 50kpot to adjust.

 

[eTech]

I used a site to help me get a equal on/off time in a period of .8 seconds. Similar to my trucks cycle. I can replace R2 (24k) with a 50kpot to adjust.

The calculator may let you do that, but in reality, the NE555 won't get 50/50 duty without special circuitry. The CMOS version is better at 50/50 duty but the drive output is very limited (max 50ma@15v).

 

[ThomsCircuit]

the NE555 won't get 50/50 duty without special circuitry.

Interesting. Well, without getting to complex is that an issue with this circuit? Would that prevent me from synchronizing the trailer circuit?

the drive output is very limited (max 50ma@15v)

You mean at pin 3 of the 555 output? If so perhaps adding a transistor to increase the output so it can drive the trailer circuit. If that's the concern.