cheap r/c 4wd toy - project.

Thread Starter

Poor old sod

Joined Jul 25, 2017
193
it has 7.4v lipo battery with usb charger -5v. assume batteries charged in parallel, and discharged in series.
expect motors get 7.4v, and Rx/servos get 3.7v as 4 wires from battery to RX etc. can anyone confirm this? large wheels will roll over small house litter. wheels plastic, may need rubber tyres for grip.
Have mounted cctv cam to front with 20,000mAh phone backup battery.
wifi cam has IR, mic/spkr, internal tracking with tilt and pan, and 64GB SD card. [7 days]. cloud compat.
Now can see/talk with who's at the door/doing what in the house without getting up. big enuf that dog won't
knock it over/out.
if reduce model to 3.7v only, will only slow motors, so less roll-over risk/impact damage. both very desirable.
will use Xeoma to view pic, may give me tracking control?
 
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Thread Starter

Poor old sod

Joined Jul 25, 2017
193
battery pack too small for b/b converter i looks just like 2 cells side by side. perhaps 500mAH? ea?
agree poor tech, but v cheap. range 50m, so Rx prob 3.7v rather than 5v, or 7.4v. Tx only 2x AA .
run time 40min. would prefer a Dalek for job, but $$ for those.
 

BobTPH

Joined Jun 5, 2013
8,804
There are 5V one cell power banks that are barely bigger than the cell, and they have a boost converter for output. So, I would not assume that. Why do you think the circuitry to switch from series to parallel would be smaller?
 

Audioguru again

Joined Oct 21, 2019
6,671
A "3.7V" Lithium battery cell is 4.2V when fully charged and is 3.2V when almost dead. Then the 3.7V rating is when it is half charged which is its selling and storage voltage.
Many Lithium battery cells are charged by a charger circuit that is powered from USB 5V.
 

Thread Starter

Poor old sod

Joined Jul 25, 2017
193
my bad-dont know where i got that.
the battery is labeled in guide as 7.4v LiPO, 500mAH. goes to a USB A connector. it is just 2 cells.
. will test USB for 2 independent cells. . parallel charge, series discharge via changing the connecting plugs? that would make the charge cable specially connected, & no supplied charger..

anyhoo, turns out camera u/s. = no pic/sound. never finishes booting. i hear cam unit difficult/fragile to dismantle. it's been in the box 6mths - new, unused. have asked ebay seller to replace, as it's Christmas. one has to hope/try.... o'wise a baby cam/similar will have to do. don't know if they work into pc/linux wifi. hope so.
 
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Thread Starter

Poor old sod

Joined Jul 25, 2017
193
pic sorted, was able to read QR code.
next point:
re-the 2 lion batteries - if they are to be charged in series, what voltage/charger should be used pls? i guess parallel charging would eliminate different charge levels if discharged in series for the motors AND as a single cell for the Rx.
NB if that assumption is correct, a dummy ballancing load can be put across the motors-only cell to reduce imballance. being a [digital?] proportional multi channel R/C system, i will assume a near constant Rx average current, independent of activity, making it easy, but this is all guesswork until i pull it further apart.
i may test it further to see if i can eliminate one cell, with only a speed penalty. 15kph indoors is too fast anyway.
if successful, one cell can run the car and camera together, making a docking station for live recharge much easier. i live in hope.

edit:
closer inspction reveals the car is hardwired to a single pair of discharge wires, so i have to have 2 batteries in series.
{
To get the camera to run on one battery only, will need a 5v voltage regulator on the 7.4[?]v, with at least 1A capacity. my biggest problem is a dual li-on battery charger.- so both batteries can be charged in series at a docking station whilst live. a box with a 2 channel r/c gymbal joystick can carry the Tx, & be powered by usb cable/psu, and sit permanently at my right hand on the arm of the chair. it will provide l/r f/r. much better than the tiny wheel and trigger on the Tx, and it will have neutral trimmers.
}
easy solution?
if i still have it, the radio gear can be replaced by my 2ch Futaba Tx/Rx pair 40.68MHz, Range >300m. It much better quality than what's in this rubbish $30-$50 car, despite is being abt 20yo and having endured their 40deg C summers. It has never been used. existing reversible ESC and steering servo can stay. the lower voltage won't cause major problems, and may slow it enough to be safe indoors It will run on one battery, [4.5v] and be much better quality than what's in this rubbish $30-$50 car, despite is being abt 20yo and having endured their 40deg C summers. It has never been used. it may need new crystals [lost?] . low v protection needed. the 12v Tx can be powered by a plugpack, and have the analog joystick remotely connected so the Tx can be mounted discretely nearby without major mods. A simple homing tracker can drive the car to the docking station for auto recharge on command or Rx off. depends on how its triggered. no carrier will do, can change from Rx control to auto homing.

auto homing:
send robo vac around house to create map, edit/transfer map & circuitry to car? car lacks obstacle dodging ability.
wonder if map based on rear wheel rotation counts, wifi'd to base station where stored as map of clear/blocked co-ordinates. some non-slp tyres called for? my learning mode could simply be just a drive from base under control around perimeters and all objects, with a go to home instruction to trigger it. Rx would need to have sufficient power. auto steering and speed from Tx. job for 32bit linux laptop without screen running an an array map. use 2x wireless mouse scroll wheels and detectors on rear wheels to count and transmit.
learning is simply be just a drive from base under control around perimeters and all objects in record mode. An auto goto home instruction will send it to dock. being wifi. i can use a remote desktop control to operate the 32 bit machine.
 
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Thread Starter

Poor old sod

Joined Jul 25, 2017
193
https://www.ebay.com.au/itm/2251606...8Ws1qWfx/CpGy2D+o6Yd6H1B1XB+|tkp:BFBM2PfBkLZh

will try to use this Tx and a modified old ball mouse to use the coding wheels on the rear wheels to make a mouse pointer move around screen. saves writing my own driver. might need more thought. x,y differences will be small but it may draw workable shapes. in straight lines will draw 45 deg line onscreen, turning will change the angle. mouse sensitivity is adjustable as pixels per pulse. open source software, so can adjust it. acceleration off.
 

Thread Starter

Poor old sod

Joined Jul 25, 2017
193
good news.
found Futaba Tx. will connect remote joystick by ethernet panel mount sockets and cable. may not bother with bsttery backup power. trouble finding metal geared analog proportional steering servo for abt 3.5v-4.5v. very old now. uk seller won't ship.
 
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