The 2010 - Single Traffic Light Driver circuit board is no longer available. It has been be replaced by the 2012 - Single Traffic Light Driver circuit board.
The information on this page will be maintained for the users of the existing 2010 - Single Traffic Light Driver circuit boards.
The circuit on this page is designed to control a Single - Three Light (Green - Yellow - Red) traffic light assembly.
The length of time that each light is lit is independently adjustable between 4 and 40 seconds for the parts values specified. The length of the ON time can be lenghtened by increasing the values of capacitors C1, C2 and C3.
The current rating of the relay contacts is 5 Amps at 30 Volts.
NOTE: The single Traffic Light circuitboard has not been certified for 110 volt operation.
When power is applied to the circuit the RED light will be ON.
Each time the RED light goes ON, the GREEN and YELLOW lights are forced OFF by resetting IC 2A and 2B via C7, R10 and Q1. This prevents more than one light being on at the same time.
See Method 1 in section 10 of the LM555 Timer page at this site for more information.
An optional, external STOP switch can be used to force the RED light ON and the GREEN and YELLOW lights OFF.
The control section of the circuit is designed to operate from a 12 volt power supply and requires 50 milliamps of current.
NOTE The Single Traffic Light Driver circuit circuit cannot properly control traffic lights at an actual intersection.
A basic intersection signal scheme would require at least 6 steps in the cycle to allow the Yellow and Red lights in opposing directions to overlap before the signal for the stopped direction changes to Green.
This circuit is derived from the Three Stage - Cycling Timer Circuit shown in section 24 of the LM555 Timer page at this site.
The following is an assembled example of the circuit board which is 2.9 inches by 3.4 inches and is drilled to fit 5mm terminal blocks.
The following table shows the parts list for the Single Traffic Light Driver Circuit. The list shows the Digi-Key stock numbers as well as the schematic part numbers
| CIRCUIT PART NUMBER | - | DESCRIPTION | - | DigiKey Part | - | Qty |
| - | - | Semiconductors | - | - | - | |
| IC 1 | - | LM555 Single Timer | - | LM555CNFS-ND | - | 1 |
| IC 2 | - | LM556 Dual Timer | - | LM556CNFS-ND | - | 1 |
| Q 1 | - | 2N3904 | - | 2N3904FS | - | 3 |
| D1, 2, 3, 4, 5, 6, 7, 8, 9 | - | 1 AMP / 50 Volt Diode | - | 1N4001DICT-ND | - | 9 |
| - | - | Resistors | - | - | - | |
| R1, 2, 4, 5, 7, 8, 10, 11 | - | 100K ohm - 0.25W | - | 100KQBK-ND | - | 8 |
| - | - | - | ||||
| - | - | Potentiometers | - | - | - | |
| R3, 6, 9 | - | 1M Potentiometer | - | 3306F-105-ND | - | 3 |
| - | - | Capacitors | - | - | - | |
| C1, 2, 3, 8 | - | 33uF / 35V | - | P5180-ND | - | 4 |
| C4, 5, 6 | - | 0.33uF / 63V | - | 495-2548-ND | - | 3 |
| C7 | - | 10uF / 50V | - | P5178-ND | - | 1 |
| - | - | Miscellaneous | - | - | - | |
| Relay 1, 2, 3 | - | Relay 5A SPDT 12VDC | - | Z2536-ND | - | 3 |
| Terminal Blocks | - | 2 Position - 5mm | - | ED1601-ND | - | 2 |
| Terminal Blocks | - | 3 Position - 5mm | - | ED1602-ND | - | 3 |
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.
Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.
08 November, 2011