New ''Dual Cell''

teamoutburst · #1 06-08-2003, 05:49 AM

Just an idea to make a dual cell with out the second cell, we could use a regulator. I have a few of these ones which i think will work, Look for the 'TPS61015'. They are really small and could easily fit into a Bit. Of corse there would need to be other components but if we did it surface mount we could keep it really small. The PCB would just go inline between the battery and the RF board it would mount on top of the RF board. The increased voltage would also be able to operate a small PICmicro which would be able to control LEDs for headlamps, you would be able to program it so when you pressed forward twice then the front lamps come on etc. I also have a few PIC 12f675s that could do this job, they are also surface mount just to be small!

AUDI-TT · #2 06-08-2003, 12:19 PM

i dont get it

TypeZer0 · #3 06-08-2003, 10:18 PM

i think this chip takes in a low voltage, as low as .8 volts, and it will bump it up to 3.3 volts max

teamoutburst · #4 06-09-2003, 01:11 AM

It simply takes in a small voltage and boosts it to something around 3v.

#5 06-09-2003, 04:22 PM

Two problems with that.

1) The extra components will make the car heavier, causing the motor to draw more current to do the work of getting it around.

2) The extra voltage is more than likely at the cost of, guess what? That's right, available current!

Interesting thought though.

teamoutburst · #6 06-10-2003, 10:55 AM

True, but im still going to have a go just to see if it does work at all.

#7 06-10-2003, 12:41 PM

Please post your results if you can.
In theory it would only reduce your run time, if you can bring the rest of it together.

ph2t · #8 06-13-2003, 03:30 AM

Teamoutburst, this is a great idea that I have been experimenting with as well.

Let's just get a few things straightend out first.

The car will increase in weight, BUT this will be less than adding another battery. The centre of gravity won't be affected as much as an internal daul cell bit, therefore keeping the car's handling in check. (Dual cell's with the batt piggybacked on the rear of the car is a waste of time, internal dual is the only way to go.)
The current WILL increase, not decrease. Ohms law will back this up.

The problem is one of supply current. I've done some tests and on a normal 1.2V battery the car pulls the following currents.

1) Fwd or Rev = approx 90mA
2) Fwd/Rev + Steering = approx 160mA
3) Car is idle = 7mA

I've designed a few converters that take 1.2V in and spit out 3.3V but none of them can supply the much needed output current for this motor and steering circuitry. The TPS61015 is only rated to 250mA for a input voltage greater than 1.8V. For a 1.2V input it would be approx 150mA. Again this is not enough. Keep in mind that increasing the voltage you increase the current. So the measurements above will probably double/triple for a 3.3V source.

I've been researching this pretty heavily and still on the lookout for a suitable DC-DC converter. Team, you can email me on ph2t@prahranpianos.com if you have any specific questions or just want to techo chat, lol! If you want I can post all the converters I've checked out to help you if you'd like. Most of them are available as free samples from all the major semiconductor component makers....

One possible application is to remove the 1.2V -> 3V converter on the RX PCB (This is used to drive the RX chip and AM receiver ONLY) and replace it with a 1.2V -> 5V step up converter. You should get a great increase in range with this mod, hmmm might go and try that tonight............

Best of luck.

ph2t.

teamoutburst · #9 06-13-2003, 12:12 PM

ph2t, what is the best regulator that you tried or seen?

tinyrc · #10 06-13-2003, 11:30 PM

Great idea guys, let us know if there's anything we can do to help; keep us posted!

BabyKiller · #11 06-14-2003, 05:39 AM

eh thats what 200mah batteries r 4

teamoutburst · #12 06-16-2003, 10:50 AM

where can you get 200mah bats from?

teamoutburst · #13 06-18-2003, 01:17 AM

WOW! thats pretty amzing to have 200mah cells in a 1/3 aaa battery, that would be perfect for testing this idea! The most ive seen is in the tiny rc shop which is 160mah (which is still an awlful lot!)

ph2t · #14 06-19-2003, 10:11 PM

Hey team, good to see this thread where it belongs. I will post some info soon on what DCDC converters I've tested.

ph2t.

teamoutburst · #15 06-23-2003, 11:00 AM

I've had an idea!

Why dont i just put the convertor inline with the motor and rc board, then it will only draw 90mah as described in one of ph2t's posts, you might not get as good steering as in normal dual cell cars, but you would get the speed!

Quote:

1) Fwd or Rev = approx 90mA