Component cost estimate

The following graphs show estimates for the component cost in Argentina if buying components for one or more devices. The prices are list prices in USD, and don't include taxes and shipping cost. For items bought in Argentina, taxes are 10.5-21%. For items imported, custom duties and taxes tend to be in the order of 15-25%, while shipping with FedEx is about USD 100 from the US. If shipping from the US with regular mail, the shipping cost drops to about USD 30, but total taxes increase to 50% of component plus shipping cost.

The cost is broken down by type of component:

IC: integrated circuits (microcontroller, illumination sensor)
pass: passive components (resistors, capacitors)
semi: discrete non-optical semiconductors (transistors, diodes)
LED: the LEDs
misc: miscellaneous components (connectors, case, battery, etc.)

If you click on the "Details" link after a graph, you can see the exact list of components, and cost calculations for different quantities.

Calculations

The first graph is for the full circuit, with serial and optical interface. Note that at 25 units, there is a significant quantity discount for the microcontrollers.

Details

The next graph is for a circuit that omits the experimental optical interface. The price difference is fairly small.

Details

Finally, this is the price if also the serial cable is omitted. This considerably reduces the cost. Note that we still include the serial interface on the main board, because a device without it would not be programmable at all.

Details

What the future will bring

Various circuit changes are planned. The most important ones, and how they affect the price:

It may be possible to use a PIC16LF87 instead of the PIC16LF88, also if the optical interface is included, which will slightly reduce the cost.
It may be possible to use an entirely different type of microcontroller. This is a longer-term project, which may lead to a cost reduction of at least 10%.
We may need a higher-quality replacement for the TS-1243 button. In this device, the button is used very heavily, and I observed one developping excessive bouncing after a relatively small number of operations. A better button will slightly raise the cost.
It may even be possible to replace the button with a capacitative touch sensor, which would be cheaper (no button), more reliable (no moving parts), and it would even simplify the case design (no button hole).

The fine print

The prices are obtained from the online catalogs of Electrocomponentes S.A. and Digi-Key. The calculations include quantity discounts and minimum quantities for items from Digi-Key. Electrocomponentes do not advertise quantity discounts, but discounts are probably available upon request. Electrocomponentes also have minimum quantities for certain very cheap components, so some of the calculations may be slightly too optimistic.

Shipping by regular mail is also available from Digi-Key, and is considerably lower in cost than FedEx, but also slower (it takes about one week, compared to 2-3 days). Note that shipments by regular mail use a different customs process in Argentina, which may require you to handle the import formalities personally at your nearest customs office, and where individuals pay a 50% tax on the sum of component and shipping cost (as opposed to 15-25% for companies or when FexEx or similar do customs on your behalf).

When ordering from Digi-Key, specify that you want to receive everything in a single shipment. Otherwise, your order may be split if any items are delayed, and you are charged for more than one shipment.

I picked these two companies because of the quality of their online catalogs. I'm a regular and generally happy customers of both, but have no interest in their commercial well-being besides that.

Note that the catalog prices may have changed since this calculation was done. Also, some prices come from a manually maintained price list, which is based on past purchases, and may be wildly inaccurate.

The price estimates include the battery, but they don't include consumables used in the build process, such as solder, acid, toner transfer paper, alcohol, flux, glue, etc. Most of these things are normally sold in quantities that last for dozens if not hundreds of projects, and I expect that people who are interested in building this circuit will already have most of these things.

If ordering components from abroad, since shipping is expensive, you may want to order some spare parts, e.g., extra chips, in case something goes wrong. It is also very easy to lose small components, e.g., resistors. They are also quite cheap, so ordering some extra supplies is generally a good idea.

Werner Almesberger 25-APR-2006