Power cut timer for rc cars

[DanB4]

Can anyone help out?

I need to control how long the user is driving the car, 5, 10, 15, 20 mins etc.

My idea is an in-line device between esc and battery connectors which will break the circuit after the selected preset time.

Can anyone help? May be some money in it too.

Cheers,

Dan

[knighthawk]

Not really an answer,
But I take it this is for a show, arrive and drive, pay a couple quid and get a minute or two !!

The only issue is safety !!
Cutting the power to the car, mid flow, will cause the car to role on uncontrolled and may cause a crash or accident !!

The easiest way is to use a small charge is the battery and let the BEC cut in, this way, normally the steering still works to bring it to a stop safely !!

But I'm no electronics expert ( obviously ) LOL

[RudolfXC]

The problem with this is that if the power becomes disconnected when the car is at full speed or on a corner, or both, you would have a spectacular accident.

[DanB4]

Yes its to control paying customers time on track.

Safety won't be a problem we're using slow brushed rtr cars with nimh cells and the epa on the throttle at 50%.

[DanB4]

Also the cars have protection and the barriers have angles on so they'll just ride up the barrier.

Saying that, a remote stop would be very cool so someone off track could choose where and when to cut power.

[DCM]

The big issue you have here is the power. The timer circuit would probably be easy to do, but it would have to cut power through a relay or similar, due to it being a power circuit. The cheapest way is a stopwatch and blocking the track.

[Jamie.T]

How about a timed circuit breaker that's used for heating swimming pools, sprinklers etc?

Or, on the very old nicad chargers some used to have a mechanical timer knob on the front which you turned to say 30mins, they had a mechanical circuit breaker which could easily handle the current without any relays etc.

[Dazzler]

Why not have a fail safe installed (and set up correctly) on the cars, then simply have the transmitters powered through an umbilical type cable from a power supply on your rostrum (no need for batteries), then make up a simple switch panel to turn transmitters off when you decide time is up. Car will drop in to fail safe..

The umbilical cables will double as security for your transmitters too..

Jamie's idea above for a simple mechanical timer switch could be incorporated in your switch panel if you so wished..

A simple push button timer switch like this may do..

http://www.free-instruction-manuals....f/p4786356.pdf

[KeithA]

a few possible options - will give it some more thought over the weekend.
1) allocate stick pack(s) relevant to time booked.
2) design/adapt existing PCB relay timer, will ask Alan to look at this for you.
3) use existing voltage drop buzzer PCB, will not stop the car but will emit a buzz
4) use WiFi receivers and adapt existing firmware for remote stops!

...depends whether you want to spend £0 per car or ££££s per car.

[KeithA]

Originally Posted by Dazzler

Why not have a fail safe installed (and set up correctly) on the cars, then simply have the transmitters powered through an umbilical type cable from a power supply on your rostrum (no need for batteries), then make up a simple switch panel to turn transmitters off when you decide time is up. Car will drop in to fail safe..

The umbilical cables will double as security for your transmitters too..

Jamie's idea above for a simple mechanical timer switch could be incorporated in your switch panel if you so wished..

A simple push button timer switch like this may do..

http://www.free-instruction-manuals....f/p4786356.pdf

The fail safe in the car and switch off the power to the tx is a great idea.

[Dazzler]

If a 2.4 radio system is used, they will most likely have a fail safe built in.. And will fail very safe, as there will be no chance of another radio being on the same frequency.

[DanB4]

Thanks all!

Keith thanks again....assuming we can spend some dosh on them within reason.

I'm reluctant for it to rely on human beings so needs to be automatic or at least for a human to be able to cut power remotely when they choose.

Speak soon,

Cheers

[DanB4]

Originally Posted by KeithA

The fail safe in the car and switch off the power to the tx is a great idea.

Yes I like that too! All cars are 2.4Ghz.

[Si Coe]

For the in-car option why do you need to cut all power? All you need if its running a brushed system is a relay switch connected to 1 of the motor wires. When the timer cuts out, the motor cuts out too, but you still have steering control as the car slows down.

Even better would be for the relay to slap a whopping resistor into the circuit, slowing the car to a crawl, and maybe lighting a big red LED on the roof. You can then get the person renting it to drive it back, saving the need for you to recover it at all.

But for reference the RC boats and trucks you sometimes see at amusement parks stop by cutting off the transmitter.

[stoff]

I'd say it depends on how strict you're being on the timing i.e "Your 5 minutes are up, CEASE!" or "5 minutes is up complete your lap".

I like a simple idea of lights on the car that are lit during use then go off when time is up. That way the person in charge can just tell the person with the lights off that their time is up and it's time to drive back to the pits.

Just read above post ^^^^ what he said!

[dev]

From an electronics point of view I'd make it work the same as the Novak smart-stop widgets, but triggered by time, not voltage.

That way it will work on any R/C electronics and doesn't have to switch high currents, you still get steering, but you have either no drive or very limited drive until you disconnect / reconnect the battery.

Could be done with just digital logic, but easier if it was a microcontroller as then you can choose things like with 30 seconds to go the epa drops to 30%, then cuts off completely.

Cost for someone to build that might not be cheap though, unless you have a mate who will do it for you. For a small electronics company it's probably at least a £500 job (1-2 days work) + parts + ~£50 cost per unit, maybe more.

Would probably be ~2 week turn around for cheap china PCB to be made too, depending on what you want the final product to look like, which limits how fast things can happen.

[mark christopher]

you just need somthing to break the signal wire from rx to speedo, you then get power for steering, as long as the device sends a neutral signal to the speedo ( im sure no signal will just give no power, ie neutral), jumper pins could be used to give different times on resrtictor

[F1END]

If you have a timing system (transponders), you could have it so that the power to the motor cuts off after the next completed lap after the 10 mins timer runs out, then have an 'exit' on the track just after the timing loop.

[DanB4]

Thanks everyone for your input and ideas

[KeithA]

Speak to Luke over at Tatooine and just get one of those R2 units installed on the top of every car. They are over 35 years old now so probably a lot cheaper and smaller than they were in 1977. Just check it hasn't got a bad 'motivator' unit or has been stolen and don't by it from a Jawa.

Sorry DDTCM