Low Cost Smoke Detector For Your Project
In fact, the assembly is largely the circuit from the freescale semiconductor data sheet.
Basic Manufacturer Specifications
- Voltage: DC 9V
- Standby Current: 10μA
- Induced Current: <30mA
- Relay Output: Normally open / closed; high / low level output
- Sensitivity: Adjustable
- Working Temperature: -5 deg C – +50 deg C
- Size (L x W x H): Approx. 2.7 x 2 x 0.7 inch / 7 x 5 x 1.8 cm
Other Specifications of Note
The relay on the circuit board is a Songle SRS-09VDC-SL. According to the data sheet, the contacts are rated for 3A @ 250VAC and 1A @ 30VDC. Coil resistance for the relay was calculated at approximately 169 mOhm.
Power Consumption Test
The circuit was powered with 9.0VDC. Testing was performed with a calibrated Fluke 85 multimeter
In the alarm state, the circuit drew 53mA and thus exceeded the manufacturer claim that it will draw less than 30mA.
Self Test Switch
The smoke detector has a self test switch. Pressing the switch will cause the red LED to flash and the relay to energize. The LED flashed within 1 one second and the relay will energize a second later.
A source of smoke was held underneath the circuit board at a distance of approximately two inches. The circuit went into alarm within about 20 seconds. When the smoke was removed, it took the circuit approximately 40 seconds to clear.
I really didn’t have a lot of luck with the sensitivity. The sensitivity potentiometer has 180 degrees of adjustment. I could not get the circuit to function when adjusting the potentiometer fully CCW or fully CW.
My recommendation is to set it mid way and leave it there.
The circuit went into alarm twice during testing for no apparent reason. In other words, the surrounding air was clear. To be fair though, these false alarms took place shortly after the smoke test. Depending on the application, additional testing could be warranted.
As previously mentioned, the circuit is largely based on the example given in the datasheet. In the data sheet, the designation give to the sensitivity potentiometer is R9. Per the data sheet….
“When R9 is used, noise pickup is increased due to antenna effects. Shielding may be required.”
The DYP-ME0010 is a solid solution for the DIY hobbyist. If you want an audible alarm during the presence of smoke, this will work fine.
Absent further testing and manufacturer quality controls and documentation, it should not be used for control in safety sensitive applications. For example, given the false alarms, you may not wish to use this for a fire suppression strategy.
At the very least, such an application would probably require that multiple devices be installed along with a voting logic scheme.
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