New ''Dual Cell'' - Page 2

teamoutburst · #16 06-23-2003, 11:01 AM

Also ph2t did you test the motor to stall when you found out the current ratings?

ph2t · #17 06-27-2003, 11:11 AM

Quote:

Originally posted by teamoutburst
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!

Tricky to do, it's not easy to be able to isolate the H-bridge transistors and run them at 3V/5V and leave the rest of the circuit untouched.

ph2t · #18 06-27-2003, 11:14 AM

Quote:

Originally posted by teamoutburst
Also ph2t did you test the motor to stall when you found out the current ratings?

Motor when stallled (enough pressure on wheels to stop motor) was about 250mA, almost 100mA more that the car at normal operations.

ph2t.

ph2t · #19 06-27-2003, 11:25 AM

Here's some of those DC-DC converters I've been checking out.

Here's the family!

Tired, gotta crash. Will post more information tomorrow.

ph2t.

teamoutburst · #20 06-27-2003, 12:06 PM

Made my first version and it is allready for soldering tonight, will post some pictures later on.

teamoutburst · #21 06-30-2003, 11:30 AM

I have managed to get pics of the PCB, I also chucked in two pictures, one of the car it is going to be fitted to, the other of the track it is going to speed around.

ph2t · #22 06-30-2003, 03:25 PM

That pcb looks mad dude, did you use a riston covered board and expose it using an overlay? Pretty darn well detailed. I'd like to know your pcb making processs. specially when you're dealing with those TSSOP packages that are so #$%^& small it's not funny!
And show us the schematic as well.....

ph2t.

BTW, the pics don't work. You need to load the URL into another browser to see.

teamoutburst · #23 07-01-2003, 01:15 AM

I have access to a cnc pcb milling macgine, so i just design it then i can mill it out really nicely, this version just ahs headlamps nothing for the motor.......yet. Its only headlamps because i just want to see how well this conertor works.

ph2t · #24 07-01-2003, 01:58 AM

You lucky @#$%^!

I've found good results for powering LEDS with the NCP1402 DC converter from onsemi.com. Datasheet is HERE .

I'm using the 5V converter, NCP1402SN50T1. I've run two high intensisty blue LEDS that need 3.6V to turn on in parallel with no problems. I think the current sink is about 50mA for the two LEDS in parallel, haven't measured it though. As with a lot of the DCDC converters a 1.2V input won't give you a great output current at the converted output. 2.4V+ input gives you more output current.

The beauty of the NCP1402 is minimal components.

There is also the NCP1450 series of converters that have a mosfet in the output stage. For a 2.4V input you can get up to 600mA, 5V output..!

Let us know how you go....

ph2t.

ph2t · #25 07-01-2003, 02:00 AM

oh yeah, forgot to say that if you need web space for hosting pics, let me know, I can help ya.

ph2t.

Azimov · #26 07-01-2003, 07:59 PM

This stuff is fascinating! BTW, do any of you have a line on a DC-DC converter that will turn 4VDC@60mA into an output of 2VDC@200mA? I've found a chip called a Buck Converter that may do the job. I'm getting some free samples in a couple of weeks so I can try it out then. But, I was wondering if you've found anything that you know will work already.

ph2t · #27 07-01-2003, 08:38 PM

Azimov, I haven't used one personally but I know they do exist. Check out all the majors, they offer free samples as well (you prolly figured that out already).

Try:

www.ti.com
www.onsemi.com
www.national.com
www.maxim-ic.com
www.microchip.com

They all have DCDC converters, PFM, PWM, buck, Inductor boost, all the buzzwords, lol!

All these sites offer free samples. It's harder to find sites for free samples for passive devices, eg caps, inductors, resistors. www.onsemi.com is also great from standard semis like, transistors, fets, diodes, etc....www.ti.com is great for logic, 74xx and cmos...

The bugger is being able to fabricate a pcb with the fine tracks to fit some of the crazy-arse packages these chips come in. Wish I had team's resources...

Anyone know of any manufactures' sites that provide free samples for passive components?

ph2t.

ph2t · #28 07-02-2003, 07:31 AM

Using the schematic I posted earlier of the NCP1402, I achieved this:

The output voltage (no LED load) is 4.97V and when I load it with 2 high intensity blue LEDs it drops to 4V. This is pretty good and I am happy with the result. The drain on the battery is about 20-30mA which is OK as well. The LEDs are wired in parallel. I didn't measure the output current from the NCP1402, only from the battery to the pcb, too slack

.

Here's a closer picture of the pcb:

This pcb has come from my
Custom FET H-Bridge projects over at bitpimps, you can check that for more info.....

ph2t.

teamoutburst · #29 07-02-2003, 10:25 AM

Thats pretty cool, the diference with mine is it uses a PICMicro chip so it can turn on the lights when you press forward twice and when you turn the indicators flash etc. Nice PCB

ph2t · #30 07-02-2003, 04:43 PM

That's great Team. I've got indicators going, it's in a thread somewhere on this site, too lazy to search, lol.

The idea of using the PIC micro is a great one, I myself have zero experience with these, post your results when you can.

I was invetigating a flip-flop/latch type of circuit that would do the same thing to be able to turn a circuit (be it lights, breaks, whatever...) on with 2 succesive clicks of the fwd button, but I'm still investigating...

Should of paid more attention in my uni days........

ph2t.