3.3v dc fan with 1.5v circuit on 1.5v power supply?

Hello all,

I have a circuit that I have ripped out of an Oust fan, which runs off a 1.5v D-cell battery and is designed to run a 1.5v dc motor (which, of course, constitutes the fan). Photos of these parts are below as attachments (sorry, no schematics...).

My questions to you all are: in place of the 1.5v dc motor fan, can I attach a 3.3v or 5v dc fan without risking the circuit? Would the fan even run? Or run, but slower (which is OK)? Or can I use a 3.3v or 5v dc fan and attach a 3v battery instead? With either of these alterations how would battery life be affected? Would I then be better going for 3v lithium battery, instead of 1.5v or 3v alkaline, to compensate or is this irrelevant? Would I blow the circuit?

The 3.3v and 5v fans I had in mind are the following:

http://au.mouser.com/ProductDetail/ebm-papst/605F/?qs=sGAEpiMZZMvuXzJ9NcThavzCYjsQ%2bSmiQSD5E/ZtD4I=

http://www.alliedelec.com/fans-motors-thermal-management/fans/?N=4294789992+4294838606

Basically I want to use a 3.3v or 5v dc fan because they have a much slimmer profile than any fan I've seen that runs off a 1.5v dc motor. I want to use the Oust fan circuit since it regulates the fan to switch on for 5 minutes every 15 minutes, which is perfect for my application. This setup is to be assembled in as small a box as possible to circulate the air and humidity within my humidor. I'd even use a 9v fan if that was a realistic option, but I don't know how battery life would go then. The fan doesn't need to go fast at all, it just needs to circulate the air in the space about the size of a large shoe box.

Your help is very much appreciated in advance, I'm ashamed I don't know these answers myself, and considerable scouring through various internet sites hasn't turned up an answer for me either! I'd love direct answers to this barrage of questions, or direction to a resource where I could work it out.

Cheers,

Paul.

Can you give us a very close up picture of the component side of the circuit board or at least some of the part #s that are present?

It's probably going to turn into an experimental "it either works or it doesn't" situation but knowing a bit more might help.

OK, so the images below are the best I could do, I only have an iphone at my disposal.

My own visual inspection determined the following:
- The round orange components are all labelled 'JF 104'
- The main rectangular black part with 14 pins is labelled 'Beagle 90011Z540'
- The black semi-circle/cylinder thing with three pins is labelled 'C9012 H452'
- The smaller black round cylinder thing laying flat on the circuit board is (as best as I could determine) labelled 'EL 1400' but there may be a letter or number before both the 'EL' and the '1400'.

I googled the information printed on the board (Model, P/N, etc.) but this didn't turn up much. If you can help my helping me interpret these different components in relation to the original questions I'd be muchly grateful.

Cheers

Hmm. Custom IC. Only one result on Google - pretty special then. Probably designed so competitors can't copy it; quite possible it's a standard chip. I wonder if the circuit will work on 3V, or if it will smoke. If you have a few spare it might be worth burning out one to see if it works.

My guess is it will run on 3V, not a lot of 1.5V only stuff running around - especially in DIP.

The JF104 is just a 0.01 uF capacitor, should be rated for at least 16V if not 50V.
The C9012 is probably representing a 2SC9012 transistor, again a made up house #
I can only assume it's all house numbered but likely good to 5V.

marshallf3 said:

The C9012 is probably representing a 2SC9012 transistor, again a made up house #

Click to expand...

9011, 9012, 9013, 9014...series are a very common low voltage transistor series in the past decades. They can be either signal, power, RF, PNP or NPN.

The 9012 in OP's circuit is a PNP power transistor driving the fan.

It is not 2SC9012, which is a NPN transistor.

The 14-pin IC is probably a low voltage MCU which provides the timing function. One of it output pins drive the PNP C9012.

I would say it will probably be OK to power it using 3.3V, but no higher. Your other options would be to power the existing circuit using 1.5V and use the output signal to drive fan of 3.3V or 5V via another transistor.

Thanks guys I love how much you know, it really is a great resource, I just wish I could give back with knowledge of my own!

I realise that since it is still a mystery circuit to a large degree that slamming 3v through it is not ideal and certainly not 100% guaranteed, but based on what you guys have said at least it doesn't sound totally nuts. I just hope nothing blows up in flames and burns my house down

Say, eblc1388, I had thought of sticking with 1.5v for everything, but instead of the power going to the fan have that 1.5v tripping some kind of voltage activated switch which would close a second circuit connected to a second battery (i.e. 3V battery) which would properly power the fan without risking the circuit. I'm not afraid to try this if plan A doesn't go well. Can you tell me what sort of switch I'd be after, i.e. what keyword to google? Any other info would be helpful.

I wish I could just do this by designing/plaguiarising and builidng my own circuit, but the skills there are just lacking too much. But I'm not afraid to solder and MacGyver my way out of this problem.

Thanks

prdaniels said:

Twell. Can you tell me what sort of switch I'd be after, i.e. what keyword to google? Any other info would be helpful.

I wish I could just do this by designing/plaguiarising and builidng my own circuit, but the skills there are just lacking too much. But I'm not afraid to solder and MacGyver my way out of this problem.

Thanks

Click to expand...

No problem. It is all the fun in electronics.

The switch you've mentioned is actually a transistor, of the type NPN which I have randomly chosen as a very commonly available transistor 2N2222A.

When the original circuit output a voltage to drive the 1.5V fan, I just reconnect this signal into the 2n2222A transistor base pin via a 47Ω base resistor and the current delivered via this resistor will turn ON the 2N2222A and current from collector pin will flow. A fan, be it a 3V, 5V or 12V can be turn ON in this fashion.

Sweeeeeeeet.

I love this ****.

Give me a moment to understand the design, if I have questions guaranteed they are coming your way.

I should add that I'm waiting for some equipment to arrive off ebay as the local electronics stores all closed down in my area a number of years ago. So if I'm a little quiet, it's only because I'm waiting on the postal service.

I've got alligator test leads, a soldering iron, insulated wire, all sorts of stuff coming my way. Can't wait to experiment. If I end up going down the path of expanding the circuit I will certainly have to go to a store, but that would be worth it with a set plan in mind.

Cheers again.

You might do something like using a CMOS 555 timer in astable mode that drives a PNP transistor's base via a resistor.

Standard BJT 555 timers won't work at such low voltage. CMOS 555 timers have very low current source ability, but can sink roughly 10x as much current as they can source. They also have much lower idle current than BJT 555's. This is why I'm suggesting a CMOS timer. When the timer output is high, the transistor (and therefore, the fan) would be off; when the timer output is low, the transistor turns on, powering the fan.

I suppose if I were going to do this, I'd use a little microcontroller, as the whole circuit would then be the uC, a couple of caps, a resistor for the transistors' base, a PNP transistor, and a "flywheel" diode for the motor. Timing would be much more accurate, and power usage would be a lot less.

I don't seem to find the minimum voltage that CMOS 555 can operate. Datasheet only mentioned guaranteed operation at 1.5V.

What about 1.45V, 1.3V...?

Well, there are perhaps a few dozen or more different CMOS 555 timers out there, and they have different specifications.

For example, TI's TLC555 has a Vcc/Vdd range from 2v-15v.
Maxim's ICM7555 operates from 2v to 18v over the commercial temp range.

Generally, they can sink quite a bit more current than they can source.

There are some 555 timers which can operate on as low as 0.8V supply. I forget the brand, anyone know? They're definitely CMOS.

I got the following from a search, 0.9V min. though..

It's not very practical to go really low in the supply voltage if you're going to use a transistor driver. Don't forget, you need to subtract Vbe from Vcc to calculate Rbase. If Vcc is 2.5v or higher, you have a wider range of reasonable values for Rbase. If Vcc is low, you'll wind up with excessive Ib when the battery is charged, and insufficient Ib when the battery is perhaps 2/3 discharged.

Hi guys,

Thanks for your help so far, I just want to ask a couple more questions about the battery I'm using with the fan. This thing is actually coming together really well.

First things first, the fan I'm using has the following specs as per this datasheet: http://www.newark.com/pdfs/datasheets/spc/75M2165.pdf

I know it says the operating voltage is between 3.5 and 6, but it seems to work fine on 3v, so it works for what I want to do.

What I'm wondering is what sort of battery/batteries would be best to use so that the fan will last for as long as possible?

The size of the battery/batteries is the stumbling block. I have looked at using 2xC-cell batteries but it just comes out too bulky. I was thinking about using a CRV3 battery (non-rechargable) which should hold about 3000mah and is the size of 2xAA's. But I'm finding it difficult to get a battery holder for the CRV3 - are they around? Why wouldn't I just use 2xAA's instead?

So I'm wondering if anyone else might have some options. Also, for each option, given the specs of the fan, what is the formula to work out how long it will run for? It will operate for 5 minutes then have a 15 minute pause then operate for 5 minutes and so on and so on.

This is harder than I thought given my non-electronics background! I wish I'd paid more attention in high school physics. Well, it looks like Mr. Hurst gets the last laugh - apart from when he gave me a C- for year 11. I'm sure he laughed then too.

Cheers, all help appreciated, and as I'm a believer in the 'teach a man how to fish' principle I'm always open to being directed to resouces... but a quick answer is also welcome if you know what I mean.

Cheers,

Paul.