The Component
Kit budgeting
So now that I've verified that the project works, I have to figure out whether I want to sell it, how many I expect to sell, and how much I want to charge. Lots of people have different techniques for this. I tend to go with my 'gut' which usually means there's a lot of information I use but its difficult to express it.
I tend to decide whether I want to sell something based on how popular/useful/easy it is. I think that this kit will be pretty popular and useful because lots of people have stuff that charges/powers over USB. Also, it seems like other people are selling similar things (like the 9V + 7805 type charger, or Griffin's 9V charger, or Belkin's 4xAA charger) It's easy to make because all the parts are through-hole and there's not a lot of them.
I'm going to basically assume I'll sell 200 or so within a few months, and I'll order parts in batches of 100, so I should budget that way. (I often buy more than 100 PCBs at a time because of the scale economies involved in PCB manufacture, as I show later.) It turns out so far that I can sell a couple hundred units of a kit in a few months, particularly if it gets picked up by a blog or web site. This may or may not be true for you, however if you cant afford to make 25 kits at once you're going to find that its hard to make any money in the process.
To figure out how much to charge, I make up a table with different quantity prices:
| Part | Price / 1 | Price / 50 | Price / 100 |
|---|---|---|---|
| Boost chip MAX756 | $4.62 |
$2.79 |
$2.32 |
| 2 x 0.1uF caps | $0.10 |
$0.10 |
$0.10 |
| 1n5818 diode | $0.09 |
$0.09 |
$0.08 |
| 2 x 100uF caps | $0.12 |
$0.10 |
$0.10 |
| 18R223 inductor | $1.42 |
$1.35 |
$1.29 |
| USB jack | $0.52 |
$0.35 |
$0.32 |
| AA holder | $0.59 |
$0.53 |
$0.49 |
| PCB | ~$12.50? |
$7.25 |
$3.75 |
| PCB tooling | N/A |
$3 |
$1.5 |
| Antistatic Bag | N/A |
$0.12 |
$0.12 |
| Sticky tape squares | N/A |
$0.10 |
$0.10 |
| Total | $19.90 |
$15.75 |
$10.10 |
These prices are for 2 PCBs, which I'll cut in two, because its cheaper (probably because they don't like dealing with very small circuit boards). I usually go with 2 week turn prices. Note that the PCB quote doesn't include the $150 one-time tooling NRE fee, which adds $3 to the /50 price and $1.50 to the /100 price. Advanced Circuits is a little expensive, but they're very good on quality and they're good at catching mistakes. Anyways, you can try going with a cheaper shop but I can only vouch for these guys.
The Board
