# Completely new at this

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
No problem. As a general rule, you want your part rated higher than your max expected voltage and current. Your voltage is a 9V battery which might go as high as 10V new, so 20V or higher adds some safety. The biggest current draw will be the LEDs. Currently, the max current draw on any one MOSFET comes from six LEDs wired in three sets of two. If we drive the LEDs at a max of 30mA, this works out to about 90mA pulled across the MOSFET. If we were to wire each LED individually, the draw would be 6 x 30mA = 180mA. So 500mA gives us plenty of room if we need it.
Alright, that helps explain it a lot!

Ah, that is why we are using the potentiometer. If you wanted to save some money and space, we could use the pot to determine what flash rate you want to stick with, measure the resistance across the pot, then replace it with a resistor. Since I assume you'll want to change the flash rate on the fly, I've added the pot. As long as it is in the circuit, you'll be able to change the flash rate on the fly. Now, I've used a square pot with a top adjustment. Since you want a low profile, you might want to use a rectangular pot with a side adjustment. In this way, you could put the pots both on one side or opposite sides of the board so the user can adjust either the red/blue or yellow/white flash rate whenever they want with a small screwdriver. Take a look at these: http://www.elexp.com/cmp_mtt1.htm.
Ahh. nifty little things lol.

Don't rush to buy the pots just yet - I want to test a few things and I might discover a wider range of adjustment by changing the pot value.
At this point, im just compiling a shopping list. I'll probablt wait till i know everything that I need for sure before i order anything. Save on shipping, just ordering at 1 time. Plus I have a couple weeks before i get any LEDs anyway...

#### elec_mech

Joined Nov 12, 2008
1,500
At this point, im just compiling a shopping list. I'll probablt wait till i know everything that I need for sure before i order anything. Save on shipping, just ordering at 1 time. Plus I have a couple weeks before i get any LEDs anyway...
Good plan!

How many of these do you want to build in time for X-mas? How about afterwards? I ask because you may want to consider making a custom board which will save assembly time. You could use the time while waiting for me to make tweeks and LEDs to arrive to learn a PCB layout program if you think a custom board will be the way to go. Once done in the program, you can send off for the boards to be made professionally or etch them yourself at home. If you're only planning to make a few, it probably isn't worth it, but if you plan make many, it will be worthwhile. Certainly not a bad thing to learn if you're getting into electronics. There are many programs, both free and not. To start out with, I'd suggest ExpressPCB: http://www.expresspcb.com/ExpressPCBHtm/Free_cad_software.htm.

Just a thought.

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
Good plan!

How many of these do you want to build in time for X-mas? How about afterwards? I ask because you may want to consider making a custom board which will save assembly time. You could use the time while waiting for me to make tweeks and LEDs to arrive to learn a PCB layout program if you think a custom board will be the way to go. Once done in the program, you can send off for the boards to be made professionally or etch them yourself at home. If you're only planning to make a few, it probably isn't worth it, but if you plan make many, it will be worthwhile. Certainly not a bad thing to learn if you're getting into electronics. There are many programs, both free and not. To start out with, I'd suggest ExpressPCB: http://www.expresspcb.com/ExpressPCBHtm/Free_cad_software.htm.

Just a thought.
As of right now, i only plan on building three or four. If all goes good i might try more, but thats all i have a need for right now.

I think maybe I'll get more into the programming a little later. Maybe some Christmas presents for myself.
I think ill start myself with the basics, then get more advanced a little later

#### Wendy

Joined Mar 24, 2008
22,176
I occasionally design PCBs. What is the biggest you could use? Include all 3 axis dimension wise.

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
Im not sure on exact specs that i need, but somewhere in the range of 4 inches wide, 1 inch deep, and height isnt too important, but we'll say 1/2 inch

#### Wendy

Joined Mar 24, 2008
22,176
Sounds like surface mount all the way then.

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
I guess now the question is... How do i go abot putting this stuff onto a circuit board? I tried downloading about 10 different programs for designing Strip boards, but some have no pre-loaded components, some i cant save, and others need some "netlist" which i have no idea what that is. The only good solution i have is a piece of paper that has the grid on it, but i have no idea what size all the parts are, until i get them.

#### Wendy

Joined Mar 24, 2008
22,176
Given the extreme size requirements you have, you don't really have too many choices.

Through hole is going to be too big, though it is my favorite. SMT (Surface Mount Technology) is all that is left.

http://en.wikipedia.org/wiki/Surface-mount_technology

It is hard to work with, but doable. Making PCBs is about the same, but easier with SMT since you don't have to drill holes for the most part.

An opps with SMT is more likely to result in parts being thrown away.

#### tracecom

Joined Apr 16, 2010
3,944
I guess now the question is... How do i go abot putting this stuff onto a circuit board? I tried downloading about 10 different programs for designing Strip boards, but some have no pre-loaded components, some i cant save, and others need some "netlist" which i have no idea what that is. The only good solution i have is a piece of paper that has the grid on it, but i have no idea what size all the parts are, until i get them.
For schematic layout and PCB design, I use and recommend DipTrace; there is a free version available for non-commercial use. DipTrace (and other PCB layout programs) has "libraries" of components that already have the sizes taken into account. DipTrace will also allow the user to design his own component "patterns" which is what I do most of the time. Once you decide what components you are going to use, you can either measure each one, record the dimensions, and use those dimensions for pattern design or PCB layout. Alternatively, you can download a "datasheet" for each component that provides the dimensions and other details; thus, you can design PCB's (or stripboards) from the individual component datasheets without actually having the components in hand.

Yes, it is a challenging process the first time through, which helps explain why someone can charge $59.95 for a lightbar kit that contains only$10 worth of parts.

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
So I guess im a little confused... I'm going to have to make a printed circuit board? And then attach my components to it? If that's right, how do I make the printed board?

#### Wendy

Joined Mar 24, 2008
22,176
Start with a schematic.

Then use a PCB drawing tool such as DIP TRACE or PCB Express.

You wind up with a graphic, 600 DPI.

From there you have options, if you remember I showed you this...

How I make PCBs

This is only one of several ways to do this.

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
what are some other ways to do it? I have no laser printer, laminator, or drill press...

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
what if the board size is not an issue? I was wondering about not having the led's mounted to the board, but instead having them attached with wire... this way i could mount the circuit board inside the car, and not have to worry about size. It could be a 4 inch by 4 inch board that way (maybe even slightly bigger)

#### elec_mech

Joined Nov 12, 2008
1,500
I want to double-check myself, but I suspect Bill's correct, fitting all the thru-hole components for this circuit on a board that size probably won't work. In th event it does, I'll let you know, but at the moment you have two options - making an SMT board and using SMT parts or separating the LEDs from the main board.

Option #1: SMT Parts and board
Pros:
Reduced time to solder parts since you won't have to cut, strip, bend, and run wires.
No need to make space and mounting method for separate LED and main circuit.
Cons:
Time to learn layout program (once done however, you save a lot of time per board)
Time/money for following - sending board out to be made professionally or buying/obtaining everything you need to do it at home, small diameter solder, small soldering tip for soldering iron.

Option #2: Separating LEDs from main circuit
Pros:
Potentially less money spent per board (at cost of time)
Cons:
Will consume a lot more time wiring from one board to another and time to add wires to run traces for each board.

Since you're only planning to make 3-4, there isn't a great deal of cost savings making a custom SMT board vs two thru-hole boards using proto boards (premade boards) in my opinion. If you think you'll be making more in the future, you certainly aren't going to lose anything by learning a PCB layout program. I'd suggest looking at Dip Trace per Tracecom's suggestion or Express PCB or both and just play with them for a few days and see what you think. You can start with a schematic layout and transfer to a PCB layout, but as this is a simple circuit, I'd just stick with the PCB layout and lay out everything manually.

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
Are there companies that will print the pcb for you? I looked a little, but I'm at work so it's not going so good. How much does it normally cost to have them done? If I am getting Pcb's, do I order normal components, or are there special ones for surface mount?

I did however find a few laser printers on Craigslist for around 20 bucks. Is there anything special I need to look for in the printer, or will any printer work? Im not having much luck with a laminator though. Found a few online for around 30 bucks.

Just trying to figure out what route to go with this. In almost half tempted to learn the programming so I can program the micro chips now. Seem like when all is said and done, I'll have the knowledge and the equipment to mass produce these things!

#### Wendy

Joined Mar 24, 2008
22,176
Yes, but it is horribly expensive.

You can draw the traces with a sharpie on the copper. This will serve as the resist, then etch it. There are lots and lots of chemicals you can use for this. Ferric Chloride is pretty save, though it stains everything and will cause metal tools to rust just by being next to them. It is available from Radio Shack. I use one part muriatic acid (33% hydrochloric acid) and one part hydrogen peroxide (3%). There are others out there too.

#### elec_mech

Joined Nov 12, 2008
1,500
I haven't made or ordered a PCB for myself, but having it made for a hobby project can get pricey. As a quick reference, Batchpcb.com through Sparkfun offers (or offered, not sure if they've changed the pricing) $2.50 per square inch. Considering you can buy a 2" x 6" proto board for about$3, it is up there. I'm sure you can find cheaper board houses though. ExpressPCB.com, PCB123.com, etc. all make PCBs. Just do a Google search for PCB.

What it boils down to is how much you're willing to spend vs. how much time you want to spend building the boards. The more time you have to work on the boards whether you're wiring them by hand or making PCBs at home, the cheaper each board becomes.

As far as laminators, Harbor Freight carries one for $30, but it was on sale tonight for$23: http://www.harborfreight.com/9-inch-hot-laminator-92499.html. They carry these in their stores, so you can clip a 20% coupon from the Sunday coupons (there's usually one every week in the Smart Source coupon flyer) and use that to save more. Print off the online price and bring it with you though - they'll honor the online prices, but they don't always have same sale in the store. Alternately, you can find them on Amazon, also about $30 or less. If I am getting Pcb's, do I order normal components, or are there special ones for surface mount? You would order SMT components, not thru-hole. Just trying to figure out what route to go with this. In almost half tempted to learn the programming so I can program the micro chips now. Seem like when all is said and done, I'll have the knowledge and the equipment to mass produce these things! That is certainly an option. It would reduce the number of components considerably. If you look at my last posted schematic as a reference, you could replace all three ICs and the non-LED diodes with one microcontroller. You'd still need the MOSFETs, LED resistors, and a couple of capacitors. This would also save quite a bit of wiring and soldering. Up to you though. Thread Starter #### 32_d3gr33s Joined Oct 29, 2011 35 I haven't made or ordered a PCB for myself, but having it made for a hobby project can get pricey. As a quick reference, Batchpcb.com through Sparkfun offers (or offered, not sure if they've changed the pricing)$2.50 per square inch. Considering you can buy a 2" x 6" proto board for about $3, it is up there. I'm sure you can find cheaper board houses though. ExpressPCB.com, PCB123.com, etc. all make PCBs. Just do a Google search for PCB. What it boils down to is how much you're willing to spend vs. how much time you want to spend building the boards. The more time you have to work on the boards whether you're wiring them by hand or making PCBs at home, the cheaper each board becomes. As far as laminators, Harbor Freight carries one for$30, but it was on sale tonight for $23: http://www.harborfreight.com/9-inch-hot-laminator-92499.html. They carry these in their stores, so you can clip a 20% coupon from the Sunday coupons (there's usually one every week in the Smart Source coupon flyer) and use that to save more. Print off the online price and bring it with you though - they'll honor the online prices, but they don't always have same sale in the store. Alternately, you can find them on Amazon, also about$30 or less.

You would order SMT components, not thru-hole.

That is certainly an option. It would reduce the number of components considerably. If you look at my last posted schematic as a reference, you could replace all three ICs and the non-LED diodes with one microcontroller. You'd still need the MOSFETs, LED resistors, and a couple of capacitors. This would also save quite a bit of wiring and soldering. Up to you though.

Thanks for the input! I think I might go the programming route. Smaller is better. Cheaper is better. Less parts means smaller and cheaper! I've got a whole slew of LEDs coming, and would love to get the rest of the parts ordered. If I program the chip, I could get the ball rolling on trying to learn that.

I wanted to keep this cheap and simple, but apparently I had no idea what I was getting myself into! Oh well. I've learned a ton so far, and I've just barely scratched the surface!

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#### Wendy

Joined Mar 24, 2008
22,176
I started off with hand drawn PCBs, you can skip the laminator and all the other steps with it.

If you draw a PCB there is likely someone on this site that can help you make a finished product.

Thread Starter

#### 32_d3gr33s

Joined Oct 29, 2011
35
For schematic layout and PCB design, I use and recommend DipTrace; there is a free version available for non-commercial use. DipTrace (and other PCB layout programs) has "libraries" of components that already have the sizes taken into account. DipTrace will also allow the user to design his own component "patterns" which is what I do most of the time. Once you decide what components you are going to use, you can either measure each one, record the dimensions, and use those dimensions for pattern design or PCB layout. Alternatively, you can download a "datasheet" for each component that provides the dimensions and other details; thus, you can design PCB's (or stripboards) from the individual component datasheets without actually having the components in hand.

Yes, it is a challenging process the first time through, which helps explain why someone can charge $59.95 for a lightbar kit that contains only$10 worth of parts.
just curious if you have a schematic for the version of the lightbar that you made up? I think i might try this route. I might as well go all in with this... Would you mind sharing the programming you had for the flash patterns? I would love to learn the programming, but having something to start with would be great!