2012 - 2 Relay PCB
The circuit on this page is designed to control a one - Three Light (Green - Yellow - Red) traffic signal assembly.
The length of time that each light is on is independently adjustable between 4 and 40 seconds for the parts values specified. The length of the ON time can be lengthened 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 circuit board has not been certified for 110 volt operation.
If there is no power to the traffic light circuit the RED light will always be ON.
When power is applied to the circuit the RED light will be ON until the first timer runs out.
Each time the RED light goes ON, the GREEN and YELLOW lights are forced OFF by resetting timers IC 2A and 2B via C7, R11 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 90 milliamps of current.
NOTE The Single Traffic Light Driver circuit circuit cannot control a set of traffic lights at an actual intersection.
A basic intersection signal scheme would require at least 6 steps in the cycle and still more would be needed 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 2.9 inches and is drilled to fit 5 mm terminal blocks.
Option 1: 1 - Bare - Traffic Light Driver circuit board is 14.50 dollars US, plus postage. (Each additional - bare circuit board is 14.00 dollars.)
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Option 2: 1 - Kit - Traffic Light Driver circuit board is 31.00 dollars US each, plus postage.
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Option 3: 1 - Assembled - Traffic Light Driver circuit board is 33.00 dollars US each, plus postage.
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If you are interested in printed circuit boards please send an e-mail to the following address: rpaisley4@cogeco.ca
Your message will be answered as soon as possible.
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 | - | 1 |
| D1, 2, 3, 4, 5, 6, 7 | - | Diode 150mA | - | 1N4148DICT-ND | - | 7 |
| - | - | Resistors | - | - | - | |
| R1, 2, 4, 5, 7, 8, 9, 11 | - | 100K ohm - 0.25W | - | 100KQBK-ND | - | 11 |
| - | - | Potentiometers | - | - | - | |
| R3, 6, 10 | - | 1M Potentiometer | - | 3306F-105-ND | - | 3 |
| - | - | Capacitors | - | - | - | |
| C1, 2, 3 | - | 33uF / 35V | - | P5180-ND | - | 2 |
| C4, 5, 6 | - | 0.33uF / 63V | - | 495-2548-ND | - | 4 |
| C7 | - | 10uF / 50V | - | P5178-ND | - | 2 |
| C8 | - | 100uF / 50V | - | P5182-ND | - | 2 |
| - | - | Miscellaneous | - | - | - | |
| Relay 1, 2 | - | Relay 5A SPDT 9VDC | - | Z1641-ND | - | 2 |
| Terminal Blocks | - | 2 Position - 5mm | - | ED1623-ND | - | 4 |
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.
30 March, 2013