Battery issue, Gas sensor project

Hi all,

I am making a gas sensor capsule but not sure which battery should I used for my project.

I used ATtiny85 for micro-controller, Transmitter ( https://dlnmh9ip6v2uc.cloudfront.net/datasheets/Wireless/General/TWS-BS-3_433.92MHz_ASK_RF_Transmitter_Module_Data_Sheet.pdf ) and Methane Gas sensor (https://www.figarosensor.com/products/2611pdf.pdf)

I tested this system with 5V from the regulator and it is working. However, I have problem with the battery as I want it to be as small as possible.

I was looking into 3V button cell battery, I guess I need 2 of them as the Gas sensor require 5V supply (I tried it with 6V using 4 AA batteries and it was working as well)

The problem comes when I see that the 3V button cell battery is said to have Maximum discharge current: 1 mA. Maximum pulse discharge current: 5 mA. while my sensor needs 56mA and transmitter needs 8mA when it is working. Will this type of battery work in my case? Are all the button cell battery has this specification? (Here is the link where I look up for batteries https://en.wikipedia.org/wiki/List_of_battery_sizes)

I really need some advice here about the recommended battery I can use for my project?

Thank you very much

Button cells will hardly work for the project. Besides maximum current, you should also think about reasonable operation duty cycles and total battery capacity.

hi..
i have gone through your data sheets... your sensor strictly require 5V.. so you have to choose battery as per this...


and other thing you should consider is that your current use of total circuit..

your sensor heater uses 280mW and as i hope your other part of circuit will consume 50mW...

so current capacity is the other thing you have to consider while choosing battery..


you need 330mW per hour approx...

So it means that it is not possible to use small battery like two of 3V button cell for the project because there is current drain limit?

Is there anyway to achieve this with this kind of battery because I really need to make this project very small (Pill-size if possible).. therefore I can't use things like AA battery.

Please help

thank you

hello...

my dear friend its our limitation to get such a battery... you can go for 9V battery(radio battery).. but you have to make some modification in your circuit...

it has good current capacity and i think its better than use AA battery.. you can try some camera battery also if you have near by you...

hope for good...

Try to use Li-ION battery (3,7V) and MAX865 chip to get 5V.

electronicsbasecom said:

Try to use Li-ION battery (3,7V) and MAX865 chip to get 5V.

Click to expand...

Thanks for your advice, I look into Li-ION battery and it looks like a good choice.

Do you think it will work if I just use Li-ION battery (3,7V) with the micro-controller and transmitter.. and when I want the trigger the sensor, I just connect DC-DC convert to pump my digital output from micro-controller to 5V to sensor?

Or should I use the converter to get 5V to the micro-controller and also make a switch between 5V and sensor which can be controlled by digital output(High/Low signal)?

Please kindly suggest.. Thanks

the sensor is using a heating coil for butane detection. its the main problem here, the batter will be drained in matter of minutes. an alternative may be , switch the sensor on for 5 secs, turn it off for maybe 15 secs and use PWM to control the heat to an optimum level.

zetinal34 said:

Do you think it will work if I just use Li-ION battery (3,7V) with the micro-controller and transmitter.. and when I want the trigger the sensor, I just connect DC-DC convert to pump my digital output from micro-controller to 5V to sensor?

Or should I use the converter to get 5V to the micro-controller and also make a switch between 5V and sensor which can be controlled by digital output(High/Low signal)?

Click to expand...

Hmmm...interesting idea...but why to do that, use the pump all the time, efficiency is quite good.

Magnatron said:

the sensor is using a heating coil for butane detection. its the main problem here, the batter will be drained in matter of minutes. an alternative may be , switch the sensor on for 5 secs, turn it off for maybe 15 secs and use PWM to control the heat to an optimum level.

Click to expand...

Like you said, it will drain the battery life so I am planning to turn the sensor on for 15-30s only (From my tested, it needed almost 30s to get to optimum heat level), then take sample and turn off the system including sensor pin for 20 minutes. That should prolong the battery life right? I'm not sure what you mean for the PWM to control the heat part though.. Please kindly explain..

electronicsbasecom said:

Hmmm...interesting idea...but why to do that, use the pump all the time, efficiency is quite good.

Click to expand...

The reason I also want to try with 1st option is because I have to turn on/off sensor in order to save battery but the the digital output from micro-controller is not 5V. So if I can just insert a DC-DC pump there, it would save the space from implementing another switch. However, I don't know if it will work or not.

So you mean I should go for 2nd option which is pumping the voltage direct from the battery to 5V and use it to supply the micro-controller. Then inserts a switch (BJT will do?) between 5V and sensor which can be trigger by digital output from micro-controller? (I have to turn on/off sensor in order to save battery)

If my understanding is not wrong, you said that the efficiency is good if I use the pump all the time? I will then go with the 2nd option then. Please suggest if the 1st option also work cause it would save space in the circuit.

PS. How about this type of battery : **broken link removed** I can't find the maximum current drain of it from anywhere.. Will this work with my project?

PS2. **broken link removed** This NiMH battery seems really good, it has high current discharge rate, I could add up 4 of them and get around 4.8V.. what do you guys think?
It also comes in the pack **broken link removed** , I can just buy 2 packs and get 4.8V..
***I'm not sure if V80H is the same model as the one in the pack. Please correct me..

Please give some recommendations

Thank you very much

Your approaching a reasonable design. 80 mAh NiMH sounds like an acceptable compromise. Li-ION energy density is higher, but the battery handling rather sophisticated.

The intended sensor operation isn't quite clear. 20 min cycles are hopefully sufficient to detect gas leaks in time, in some cases (e.g. defect LPG installation), they probably won't. And about 2 days of operation isn't mind blowing.

you can control the heater temperature by driving it with a transistor. the base of the transistor can be connected to the pwm pin of the controller. You can turn on and off the sensor and can prevent overheating the sensor.

Magnatron said:

you can control the heater temperature by driving it with a transistor. the base of the transistor can be connected to the pwm pin of the controller. You can turn on and off the sensor and can prevent overheating the sensor.

Click to expand...

So something like analogWrite(0) for off, analogWrite(255) for on

Can I just use digitalWrite High/Low instead of PWM to turn on/off a transistor?

yeah, if you are using arduino, its analog write you can change the duty cycle to control the heating. if you use analogWrite(255) its equivalent to turning it ON. and an**(0) will turn it off. do some simulation work in proteus.

zetinal34 said:

Like you said, it will drain the battery life so I am planning to turn the sensor on for 15-30s only (From my tested, it needed almost 30s to get to optimum heat level), then take sample and turn off the system including sensor pin for 20 minutes. That should prolong the battery life right? I'm not sure what you mean for the PWM to control the heat part though.. Please kindly explain..



The reason I also want to try with 1st option is because I have to turn on/off sensor in order to save battery but the the digital output from micro-controller is not 5V. So if I can just insert a DC-DC pump there, it would save the space from implementing another switch. However, I don't know if it will work or not.

So you mean I should go for 2nd option which is pumping the voltage direct from the battery to 5V and use it to supply the micro-controller. Then inserts a switch (BJT will do?) between 5V and sensor which can be trigger by digital output from micro-controller? (I have to turn on/off sensor in order to save battery)

If my understanding is not wrong, you said that the efficiency is good if I use the pump all the time? I will then go with the 2nd option then. Please suggest if the 1st option also work cause it would save space in the circuit.

Click to expand...

Ok, I checked typical supply current of MAX865 pump and it is 0,6mA and it is quite large for this system. So, using the pump only for reading sensor is not bad idea. But, you have to know next: uC can work with Li-ION battery only if you implement sleep mode, next...you have to use analog switches for turning on transsmiter and sensor (easiest just allow power to pump and sensor)...my recommendation for switch is MAX890LESA because of 0,1uA conssumption, and the most important thing, you have to set refference for ADC of uC, if you use LI-ION direct on uC, reference will be variable.

electronicsbasecom said:

Ok, I checked typical supply current of MAX865 pump and it is 0,6mA and it is quite large for this system. So, using the pump only for reading sensor is not bad idea. But, you have to know next: uC can work with Li-ION battery only if you implement sleep mode, next...you have to use analog switches for turning on transsmiter and sensor (easiest just allow power to pump and sensor)...my recommendation for switch is MAX890LESA because of 0,1uA conssumption, and the most important thing, you have to set refference for ADC of uC, if you use LI-ION direct on uC, reference will be variable.

Click to expand...

I actually program the uC to turn on and off its output pin when needed already eg. turn on transmitter just for 1s to transmit then sleep).

Do you think I still need a switch as I can control the voltage of the pin which connected to the sensor?

thank you

You need switch for gas sensor, at least very simple since he can be represent as resistor it will be consume energy if there is a voltage on sensor