Using an LED array
From Open Source Urbanism
In order to make the display more readable at low speeds we could look at using multiple lines of LEDs. Probably the neatest way to do this would be to use an LED matrix like the 5x7 Dot Matrix display here or here.
The first matrix linked to above has pins for the rows and columns; we could probably use the scanning method outlined on this page. The second matrix has a common anode so we would probably need to use a shift register IC to address all of the LEDs. The first method is preferable (lower component count and cheaper) however it will use most of the Arduino's 14 output pins. We could of-course use a shift register with this matrix also, and probably the best approach is to use individual Arduino pins to access the 5 columns and an 8-bit shift-register IC to control the rows. With this method you could address two 5x7 matrixies (for left and right hand side of the bicycle wheel) from a single Arduino board with a single 8-bit shift-register.
I just ordered the following from Futurlec (I've never ordered from them before but they have a great range, they do small orders and are a lot cheaper than anywhere else I've found).
| Part Number | Description | Qty | Price (AUD) | Total (AUD) |
|---|---|---|---|---|
| 74HC595 | 74HC595 - 8-bit Ser-to-Par Sh. Register | 6 | 0.60 | 3.60 |
| LEDM57G | Green 5x7 LED Matrix Display | 2 | 1.56 | 3.12 |
| LEDM57O | Orange 5x7 LED Matrix Display | 2 | 1.56 | 3.12 |
| LEDM57R | Red 5x7 LED Matrix Display | 2 | 1.68 | 3.36 |
| UGN3503U | UGN3503 Hall Effect Sensor IC | 4 | 1.80 | 7.20 |
| Sub-Total (AUD) | 20.40 | |||
| Shipping (AUD) | 4.00 | |||
| Total (AUD) | 24.40 |
