Tiny batteries and PICAXE ma

[jadesteffen]

How many mA would the picaxe 18x draw if i used transistor interfacing circuits on all outputs.

also would it run on 3 volts?



Edited by - jadesteffen on 10/7/2005 6:54:31 PM

Edited by - jadesteffen on 10/7/2005 6:55:04 PM

 

[Michael 2727]

How long is a piece of string,,?
What type of loads do you want to run, this
will have the biggest influence on the amount of current needed, high current loads
= more base current.
If your supply was 5V you could use small MOSFETs, they draw virtually no current
just voltage to switch.

 

[BeanieBots]

As stated by Michael 2727, it is impossible to say without knowing the type of transistor and how hard you will be driving them. The PICAXE itself draws around 1mA in normal operation. This will increase if overclocked and can be reduced by under clocking and/or using sleep.
PS
M for Mega, m for milli.

 

[jadesteffen]

I would be using small pager motors, and I think that they draw about 300 mA or so.
I'd like to use the smallest possible amount of current.

 

[Bloody-orc]

mesure the exact amount of current they draw so we can give you precise time.

 

[manuka]

300mA=splutter!! If you want cheap energy efficient motors then consider the so called 3V &quot;Solar&quot; motors sold by the likes of Dick Smith for ~$2. These draw only ~30mA unloaded, handle PWM well, revolve slowly (max 1000rpm) and amazingly still work on as low as .6V. Driving by a simple NPN transistor from a Picaxe output is a breeze. See =&gt;www.picaxe.orcon.net.nz/motorpwm.jpg <A href='http://www.picaxe.orcon.net.nz/motorpwm.jpg ' Target=_Blank>External Web Link</a> Stan

EXTRA: After rereading your post- are you really after tiny motors (instead of tiny batteries)or do you want energy efficient ones? The battery game of course is a HUGE field with numerous avenues. What are you trying to do !?

Edited by - Stan. Swan on 10/7/2005 8:14:31 PM

 

[Michael 2727]

300 mA sounds way to much for a pager motor.

More info would be a great help.

 

[jadesteffen]

I'm looking for really small, energy efficent motors. Maybe 300 mA is overkill.

I bought some tiny 3V, polyacene batteries from Elect-goldmine. I don't know just how much current they produce.
The reason I'm getting everything so tiny, is cause I'm building a tiny 1&quot; square(or smaller) robot. It'll have 3 IR proximity sensors, a light sensor, solar panel and maybe a line seeking function.

on a side note, does anyone know how to charge one of those little batteries?

http://www.goldmine-elec-products.com/prodinfo.asp?number=G13133&amp;variation=&amp;aitem=1&amp;mitem=2

 

[BarryP]

Going By The Link , They are .6 Farad Caps with 20Ohms Internal Resistance.
You could check out a small pdf on charge/discharge capacitors.
http://www.rowan.edu/colleges/las/physicsandastronomy/LabManual/labs/Capacitor.pdf

 

[Michael 2727]

A couple of years back I tried a little
project using a PIC 509, I have 2 windowed
erasable units.
I was using an ELNA 5V 1Farad cap for the
power supply.
The unit just flashed 2 LEDs alternately very briefly at around 1/2 second intervals.
The cap took around 4 1/2 mins to reach
full charge (85% in the first few seconds
though) I was getting about an hour of use
out of it. The LEDs were only drawing 2mA or so and very briefly flashed.

With a 3 Volt cap, the Picaxe probably won't last long when the voltage drops,
caps are not quite like a battery discharge
wise. And a motor will flatten the cap quite
quickly. The Super caps are mainly designed
to hold memory power in a supply failure.

You may be better off using button NiCads or
NmHi.

Do some charge/discharge tests on your Cap
to see what it will deliver.
When charging the last 15% takes 10 times
longer to get to full voltage.

Good luck.

Sorry 2nd question.(charging)
I just connected mine to the 5V supply and
waited. No resistors no anything.
Don't charge with more than the Max Rec voltage though, did you get a data sheet ?


Edited by - Michael 2727 on 10/7/2005 10:44:02 PM

 

[premelec]

I've got some of these units I use to back up memory - they are NOT good for high current discharge or long term storage of charge. At .1 amp you are going to get .1 x 20 ohms voltage drop as well = 2 volts!

Find some tiny NiCd or NiMH - some spent cell phone packs might have very small NiMH by the looks of their size - be careful dis-assembling the batery case - I've not seen anything in the 1&quot; sq range but I expect they are there somewhere... remember batteries may contain dangerous corrosive materials.

 

[ljg]

I have seen nano robots ( robots &lt; 1&quot; cube) that use these batteries--

E-Tec 90mAh Lithium Polymer single
cell 3.7v Dimensions: 23mm x 14mm x 5mm, Mass 2.2g

ingenious design allows threee of these to be placed inside the robots along with all the other bits.

The main drawback is that the batteries require a special charger. improper charging can lead to explosion and fire. I use larger versions of these on a couple of my robots and take the precaution to place them in a Pyrex bowl for charging and have salt water ready to dowse any flames.

running the batteries down too much can also lead to their destruction (no flames, they just stop working)

 

[BeanieBots]

I'm with Larry on this one. They look like lithium polymer and if so, should not be played with unless you know what you're doing. Besides, as pointed out by premelec, they are not suitable for your application.

Your initial thread indicated that you were only interested in the PICAXE current, implying that load current would come from somewhere else. If it is your total project current that you are interested in, then the PICAXE will draw so much less than the other bits it will not play a part. Your IR range sensors for example will draw several tens of mA.

If you want to play with micro robots, check out &quot;BEAM Robots&quot; by Mark Tilden (hope I spelt that right). For solar powered robot, start with the panel and determine how much power is available and at what voltage it is presented. This is not any easy field to start in because EVERYTHING in such a robot is absolutely critical. The brightness of an LED can be the difference between success and total failure. How much POWER will your panel give? Is that enough to move the weight of your bot even assuming 100% efficiency?
Might I suggest a much easier project such as a robot about 6&quot; cube running from AA batteries as a starting project. You will then get a &quot;feel&quot; for what is and what is not possible. Motors for example, can now be obtained that are in excess of 98% efficient but you will need a mortgage to get them. The motors found in toys are so cheap that their price is negligeable but they are only around 20% efficient.

 

[jadesteffen]

i plugged one of these into a tiny solar cell(.235 V) and set the timer 30 minutes. so far, it's fine. in 10 minutes I'll see if it worked or not.

 

[manuka]

.235V ? Most PV give out .5V a cell in bright sun of course. I'm also with the others on this, since you look to be pushing the envelope on just TOO many technologies. Unless you have a NASA type budget I'd suggest you think bigger &amp; use available resources. 3 xAAA NiMH rechargeables (1.2V each ~900mAh)are normally the smallest viable electro. chem cell for most projects (&amp; -ahem- budgets!). They'll deliver serious currents too,while of course their energy store lasts... Stan

EXTRA: Lithium, although not quite as explosive as other alkali metals such as sodium,is MOST enthusiastic about water. See =&gt;<A href='http://en.wikipedia.org/wiki/Lithium ' Target=_Blank>External Web Link</a>. Salt/sea water may be safer than fresh for controlled taming,as LiCl may form, but it's still seen as very hazardous by many Li-Ion battery makers. Suggest you tame any battery flames/explosions other ways !


Edited by - Stan. Swan on 10/8/2005 7:52:01 PM

 

[hax]

Some rechargeable &quot;cordless phone&quot; type packs are quite small. They use small NiMh cells. Three cells gives 3.6V and is just under 1&quot; square.

There is a panasonic range that has what looks like three large button cells shrink wrapped together. Might be worth investigating.

 

[Auda]

How long is a piece of string,,?
This has been asked before, its 2'6&quot;
Auda

 

[premelec]

damn... I thought it was .762 meters...

 

[ljg]

actually, Stan, the recommended disposal method for LI-PO batteries is puncturing the bag and soaking the contents in salt water. The standard way they fail from overcharging is that they puff up like a marshmallow. and get hot.Though fire is theortically a possibility, they aren't considered flamable like Litium -Ion technology.

see

http://www.answers.com/topic/lithium-polymer

 

[bkf11]

A late rely to this post... I have a micro remote controlled car the size of a toy car (5cm long?) which uses NiMH (maybe NiCD) button cells to charge/power it. 3 cells = about 3.5-4V ran a Picaxe 18x but some unpredictable behaviour (ADC didn't work so well). This was bought for NZ$20 or so so pretty cheap source of rechargeable button cell batteries
I was trying to control the car with the Picaxe by soldering contacts onto the car's micro pins. Got it going but it could not sense obstacles with my IR LED/IR phototransistor pair which works at normal voltage. Sitting in my cupboard now...