Maker Pro
Maker Pro

Need a simple circuit to reset a device very X minutes

supak111

★ƃuᴉɯǝɥɔs sʎɐʍlɐ★
Apr 29, 2012
341
Joined
Apr 29, 2012
Messages
341
Hey guys looking for a simplest circuit to just power cycle a 12v device OFF and back ON even say 5 minutes. Is there any simple off the shelf module that can do this? or perhaps a simple circuit that can?
 

supak111

★ƃuᴉɯǝɥɔs sʎɐʍlɐ★
Apr 29, 2012
341
Joined
Apr 29, 2012
Messages
341
Thanks Harald. I was hopping for something super cheap and simple as I might try selling this gadget once finished.

Digital timer is too expensive, it would add too much cost unfortunately
 

SalRu

Mar 16, 2017
12
Joined
Mar 16, 2017
Messages
12
Hello,

I am not sure this solution can be suitable for you..

But what about using a monostable with NE555 and a transistor to drive the output?


Hope to be helpful!
 

supak111

★ƃuᴉɯǝɥɔs sʎɐʍlɐ★
Apr 29, 2012
341
Joined
Apr 29, 2012
Messages
341
At most few dollars and hopefully it isn't big like the timer. Btw this is only restarting a tiny bluetooth module which doesn't drew much current at all.
 

SalRu

Mar 16, 2017
12
Joined
Mar 16, 2017
Messages
12
If the blt module has a reset pin the 555 should be the best option!

Anyway you can try to supply the module through the 555 monostable and see what happens:)
 

Bluejets

Oct 5, 2014
6,984
Joined
Oct 5, 2014
Messages
6,984
If the blt module has a reset pin the 555 should be the best option!

Anyway you can try to supply the module through the 555 monostable and see what happens:)
If this needs to operate on a continuous basis, ie off, on, off, on etc then the op will need to look at astable configuration.
 

supak111

★ƃuᴉɯǝɥɔs sʎɐʍlɐ★
Apr 29, 2012
341
Joined
Apr 29, 2012
Messages
341
Yea I was thinking about using the 555. I think I just figured something out even simple and cheap. There are these $1 555 delay timer modules with a relay on them. I have a few at the house.

What if I connect it like this picture. The timer would count off say 5 minutes, it would activate the relay and because of that it would cut power to itself and restart the 5 minute countdown again...

2rzw8b4.png
 

AnalogKid

Jun 10, 2015
2,913
Joined
Jun 10, 2015
Messages
2,913
Not nearly enough. The timer changes state when the timing capacitor is charged up (to 1/3 Vcc). If you then remove power to the timer, the 555 cannot discharge the cap.

There are adjustable and programmable cycle timers on ebay that will do what you want, but 1 second out of 300 is a very high duty cycle. This is one of the reasons I don't like the 555 for multi-minute periods, but it can be done. A modified version of the standard 555 astable can be tweaked to a 300:1 duty cycle, but the timing cap will be huge and the long period will vary with room temperature.

Another way uses the CD4060 to make one pulse every 256 counts. A 5 minute cycle would produce a 1.2 second pulse.

ak
 
Last edited:

supak111

★ƃuᴉɯǝɥɔs sʎɐʍlɐ★
Apr 29, 2012
341
Joined
Apr 29, 2012
Messages
341
Yup just tested this and it wont work. OFF state is too short like you guys mentioned so when the module comes back ON it only holds ON for about 10 seconds instead of 300 probably because the cap is still full.
 

AnalogKid

Jun 10, 2015
2,913
Joined
Jun 10, 2015
Messages
2,913
What to you want the output of the timer circuit to do:
1. Toggle a reset pin on the bluetooth device.
2. Open the 5 V or 3.3 V supply to the device.
2. Open the GND to the device.
4. Other.

ak
 

supak111

★ƃuᴉɯǝɥɔs sʎɐʍlɐ★
Apr 29, 2012
341
Joined
Apr 29, 2012
Messages
341
Device is a BT module with a relay on it (proximity-switch), its not just a simple little BT module. I want to keep the BT in discovery mode and that only happens first 5 mins I believe. Just cutting power to the whole device puts it back to discovery which is my goal.

BT module on it is a rda5851s I believe. If I could just reset the BT module that would be great but I cant seem to figure out what pin the reset is nor would it even reset it back into discovery mode if I did find the reset pin.

Ill take some pics of the whole device with the rda 5851s on it soon.

For now what about this:

2jb1tp2.png
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Simplest (for a certain definition of simple) would be a 6 pin microcontroller. It may be able to power the Bluetooth device from is output pin. If not, add a MOSFET and a resistor.
 

Bluejets

Oct 5, 2014
6,984
Joined
Oct 5, 2014
Messages
6,984
So like AK says, what do you want the circuit to do?
If continuously cycle on and off you could use the 555 in astable mode.
Set your on off to whatever via rc arrangement on 555 terminals 6,7 and 2.
Forget your wiring arrangement that cuts power to the timer, leave it powered and run your bt from the relay only.
No??
 
Top