Separate Brake Light From Turn Signal

eTech said:
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.
Click to expand...
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.
 

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.
 
eTech said:
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.
Click to expand...
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.
 
As you still considering also building the circuit I proposed, or are you just going with this one?
 
crutschow said:
As you still considering also building the circuit I proposed, or are you just going with this one?
Click to expand...
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?
 
ThomsCircuit said:
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
Click to expand...

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.
 
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?
 
ThomsCircuit said:
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?
Click to expand...
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.
 
Last edited:
eTech said:
If there is no pin, and a thru hole connection is needed, then the hole should be an ordinary via.
Click to expand...
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.
 
eTech said:
Thermal pads are intended to act as a "thermal conductor" so that the pin can be heated enough to be soldered.
Click to expand...
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.
 
crutschow said:
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.
Click to expand...
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.
 
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.
 
ThomsCircuit said:
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.
Click to expand...

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).
 
eTech said:
the NE555 won't get 50/50 duty without special circuitry.
Click to expand...
Interesting. Well, without getting to complex is that an issue with this circuit? Would that prevent me from synchronizing the trailer circuit?
eTech said:
the drive output is very limited (max 50ma@15v)
Click to expand...
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.
 
You must log in or register to reply here.

Similar threads

D
  • Question
Led light turn on at specific Voltage
2 3
Replies
43
Views
10K
Tex260Z
T
led light bulb component
Replies
4
Views
738
aliarifat794
A
  • Question
Controlling a LED from lower voltage signal
Replies
11
Views
4K
Pommie
P
R
  • Solved
Cant Light up UV lightbulb!
Replies
8
Views
2K
ZipZapOuch
  • Question
Filtering for a signal level detector
Replies
12
Views
2K
throbscottle
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…