RS-5610 gas sensor
- Thread starter Denzel
- Start date
I've never used one with PICAXE; only a similar one in conjunction with a volt/comp many years ago.
I can't see any real problem. The sensing wire changes resistance in relation to concentration (gas not yours). So the voltage developed across RL changes. You may (not sure) have to buffer it with an op-amp, which also gives you the opportunity to increase sensitivity if needed.
Your supply voltage will have to be very stable and note the current consumption, there are other devices 'out there' with much lower consumption figures. And your PICAXE supply needs to be bang-on and smooth too for your reference.
The one I used had a similar spec to this and I used switched-mode to get working current consumption down as I was using it in a caravan from a 12V battery. Worked well, and then of course you'll have to calibrate it.
Remember to put a bit of lag/hysteresis in your code, in a similar way that CO detectors use. (There are 'official' figures for those but I can't remember them).
Don't be scared - just try it. Good project. I've been thinking about doing one for ages but never got around to it. Let me know how you get on.
I can't see any real problem. The sensing wire changes resistance in relation to concentration (gas not yours). So the voltage developed across RL changes. You may (not sure) have to buffer it with an op-amp, which also gives you the opportunity to increase sensitivity if needed.
Your supply voltage will have to be very stable and note the current consumption, there are other devices 'out there' with much lower consumption figures. And your PICAXE supply needs to be bang-on and smooth too for your reference.
The one I used had a similar spec to this and I used switched-mode to get working current consumption down as I was using it in a caravan from a 12V battery. Worked well, and then of course you'll have to calibrate it.
Remember to put a bit of lag/hysteresis in your code, in a similar way that CO detectors use. (There are 'official' figures for those but I can't remember them).
Don't be scared - just try it. Good project. I've been thinking about doing one for ages but never got around to it. Let me know how you get on.
...
Hey thanks.
I think ill see how it goes without the op-amp for now and see how the readings come out. Ive had problems in the past i.e reading battery voltages when using the readadc and the picaxes voltage has been lower/higher than expected and therefore the result was not correct so ill have to work on this and perhaps utilise a 5v regulator.
Thanks
Hey thanks.
I think ill see how it goes without the op-amp for now and see how the readings come out. Ive had problems in the past i.e reading battery voltages when using the readadc and the picaxes voltage has been lower/higher than expected and therefore the result was not correct so ill have to work on this and perhaps utilise a 5v regulator.
Thanks
Definitely use a regulator for PICAXE as that 5V is used for your ADC reference. Use a separate one for the gas sensor, whether linear or s/mode up to you.
Linear types smoother. S/mode more efficient but 'noisier' (though this is very much in 'your hands' as PCB layout can make a huge difference to s/mode performance). Many people, strangely, fail to read Data Sheets which give essential advice on pcb layout and component specs.
I know I bang on about s/mode, but for battery stuff (and if your circuit can live with a bit of noise) s/mode are far better, but more expensive and harder to get right. Also if you are dropping from higher supplies (e.g. a 12V car battery ) and using a fair old current then the efficiency gives 2 main benefits. 1. Cooler running 2. Less current from your supply.
Yes, breadboard it up without an op-amp. After all, it won't explode...
Linear types smoother. S/mode more efficient but 'noisier' (though this is very much in 'your hands' as PCB layout can make a huge difference to s/mode performance). Many people, strangely, fail to read Data Sheets which give essential advice on pcb layout and component specs.
I know I bang on about s/mode, but for battery stuff (and if your circuit can live with a bit of noise) s/mode are far better, but more expensive and harder to get right. Also if you are dropping from higher supplies (e.g. a 12V car battery ) and using a fair old current then the efficiency gives 2 main benefits. 1. Cooler running 2. Less current from your supply.
Yes, breadboard it up without an op-amp. After all, it won't explode...