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Nice work dude. Need to concentrate more on steering than on flashing your light 😉 show off!!
Been looking at this for a while. At least I now know it DOES work!! I have a NOS design in the pipeline (using capacitor) for some months now. Now to find time…aaahhhh!!
HR, you are correct on the 2.5v limit stuff (although it doesn’t completely kill the batt if you drop below this!) Since the batts hold a resonably flat discharge curve (same as NiMH) you can fairly easily tell when the voltage drops! As a rule of thumb as soon as the car drops speed you can recharge (doesn’t matter when you charge Li cells ie. part charge). Just make sure you have a decent charger! The cars are close to the limit for the max discharge rate so if you are running at full throttle the whole time you may run into some longetivity issues!
Fast as all hell! Hardest part is keeping it in a straight line when at full stick! With stacked FET’s, KIT racer gears and 3.8 motor I have pulled a 5m wheelstand. It almost runs out of range before hitting top speed!!
Thats why you put low gears on so there is little load on the motor! the higher the load the quicker you kill the motor.
Still got about 30 lying around but if I run out I will let you know!
Once I get Protel reloaded in the computer (Had a virus and had to format my HD!) I will send you the PCB diagram. You at least give me an excuse to get on with the job and finish what I started:smiley2:
The top ones on that page are the ones I use. Yes in a BCG and my Bit char plane.
Yes the plug needs to be soldered to the board. It is a tight fit and with a bit of modification it can be done internally.
You spend a fair bit of time on your roof!! Once you get the handling down pat you get the hang of it. Works best with a booster car as you only use boost on straights. Would be a good option for those of you with monsters and want to use low gears for torque without loosing out on speed!
Ok. All of these relate to the schematic on the MAX712/713 Data sheet!
At Ifast = 200mA (4C for 50mAh, 2C for 100mAh, 1C for 200mAh)
For the number of cells:
No of Cells : PGM1 : PGM0
1 : V+ : V+
2 : open : V+
3 : Ref : V+
4 : Batt- : V+So from this you can setup a 4pole switch between PGM1 and the options.
For a timeout of 66mins, with deltaV termination; Leave PGM3 open and tie PGM2 to V+
The power disipation of the transistor = 2.16W
To choose a value for R1 use:
R1 = (min transformer voltage – 5V)/0.01
R1 = 800R to 1k2 if using a 12v transformer.Rsense = 0.25/Ifast = 1.25R
All this should make sense I hope. Any Q’s ask.:D
Not sure as I got mine from Plantraco! Nothing local stocks them or would get them in. Hard to find ones this small is the problem. Anyone else have these??
Looks like Plantraco have new batts since I lasted looked. They now have a 170mAh version at 5grams. They also have a charger there if you want.
You can get Li batts that work on a BCG. They are 3.7v so equivalent to a tricell car. They also only weigh 4g which is heaps less than NiMH batts. At 145mAh it is slightly less capacity than NiMH batts but you get the higher voltage. You just need to have a Li charger to charger the batt. Plus if you are on a budget the Li cell tend to cost a bit!
Ph2t, yep back in the hood!
The beauty of the MAX712/713 is they supply the batteries load as well as charging the batt!! So this chip is perfect for the bit-chars or any other batt that needs to be charged in situ. I have all the R values at home for 50mAh Nicad, 150mAh NiMH, 200mAh NiMH charged at a “safe” rate and all pin connections if you want them. (they may be the same as in the schematic above….just don’t know them off the top of my head.)
I too have to find time to finish this project (I have the board printed ready for etching). Will hopefully have done by next week and let you know how it goes.
Pretty damn cheap DeltaV charger if you ask me. Those chips go for $30ea from RS I think too.
Just follow the schematic. You can’t go wrong! Get the data sheet from http://www.maxim-ic.com You can use the MAX712, MAX713 for NiCad/NiMH or the MAX846A, MAX745 for Li batts. You can get FREE samples of these sent right to you door. Note: the MAX846a and MAX745 are smd compontents so you will need to be handy with a soldering iron.
Farnell are generally cheaper but RS Components have a bit better choice in the hard to get parts!
http://www.rs-components.com.au ($10 next day delivery)
http://www.farnell.comIf you hadn’t work that out all ready:smiley2:
The black came in a Lxx modellista with 3.0 on the box but the box was open so not sure (from toyeast). Two of the white ones came in the bit battle set with 1.6 on the box. The 3.5 is definitely 3.5 but perfection not tomy! I have a red 3.0 but that was from a z-car! I would say the orange is a 2.6 then.
(would a pictures help?)
Cool thanks for your help so far!
now all you need is the cop bit char g and that is one sweet mod!
At about $AU35 to $40 (without meter which costs an extra $28) it is not the cheapest thing. I am going to make a few for some mates who just want a set charging rate for like $15. I am keen to get my Li cells and make up a similar charger with the MAX chips. I am going to need some help since there is like 3 types of Li cells!
As promised, my first current reg charger.
Presetable countdown timer (via DIP’s), charge/discharge switch, variable current, ammeter, auto off with buzzer and indicator light. Has cooling fan as I only used small heat sinks.
This is NOT the delta V charger but a simple timed current regulator!
p.s. Thank you uA for you FET mod site (as you can see this lxx is FET modded). Wouldn’t have done it without your explanation.
Cheers – Ads
Yes you are right. The fact that they all need to be the same is the problem. I know my racing buddies all have different setups so I was only thinking parallel charge. sorry for any confusion.
Dave, the trouble with going to lots of cars on the one charger is the AC/DC transformer. Unless you are happy to put them on for a couple of hours (which most of us are too impatient to do) you will need a pretty big trans. For instance, you want to charge 4 150mAh bats in 30mins you will need a trans capable of at least 1.6A. For 10 cars thats at least 4A! Allowing for some losses!
As for a timed charge, my first Bit CharGer was a timed current reg with LED countdown timer. This is a very simple circuit and I will post a pic later when I get home. Might be more what you want for same charge in many cars.
uA, which Li batts you using and from where?
ph2t, sure thing dude, just hope I can help as i am only new the whole Bit thing! I really want to get a nice developed Li charger and possibly a microcontrolled multichem charger:shock:
uA, which Li batts you using and from where?
ph2t, sure thing dude, just hope I can help as i am only new the whole Bit thing! I really want to get a nice developed Li charger and possibly a microcontrolled multichem charger:shock:
one thing I didn’t say was where to get the free ones…duh. you get the 2 free samples from http://www.maxim-ic.com they are the manufacturer. I am thinking about getting there LiPo chip so I can do the 3.7v mod.
ph2t, can you get the delta v chips from dicko’s or are you just talking the circuit components??
If you are fairly electronically advanced you can make you own delta V charger for real cheap (i spent about $AU10 on parts). This can be fully customised to work with 1 to 26 cells and charging current for C/4 to 4C. I have set mine to switch off at -5mV and it works fine for these small cells. It does not get false reading from the car circuitry as it supplies the circuitry as well at the batt. Use the MAX712 or MAX713 chips. They will GIVE you 2 sample chips for NOTHING. thats right, nothing. you don’t pay shipping or anything. The chips retail for around $25ea on rs components and that excludes GST. Just an idea for the techies out there.
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