Colvic Watson
Well-known member
Lots of 12v timers out there but I want one to control a coolbox running 15 minutes on, 30 minutes off. Something like this but 12v.
Any ideas?
Any ideas?
Do 12v timers like this exist?
- Thread starter Colvic Watson
- Start date
hightech
New member
There are, but not in the same price range as the £1.99 diy ones.
Have a search on R-S http://uk.rs-online.com/web/search/...Section&N=4294964207#Timers and Time Switches
Maplin may do something as well
Have a search on R-S http://uk.rs-online.com/web/search/...Section&N=4294964207#Timers and Time Switches
Maplin may do something as well
Colvic Watson
Well-known member
Tried Maplin and the site you quoted and no luck, thanks anyway.
MonniotC
Member
What's to stop you from using the 240v one in a 12v system?
MonniotC
Member
Er....Just realised.
MoodySabre
Well-known member
There's this which appears to be the same as this for a better price. Max 8A.
ianj99
Active member
Rapid do this one:
http://www.rapidonline.com/netalogue/specs/48-0780.pdf
http://www.rapidonline.com/Electron...-function-plug-in-timer-module/61787/kw/timer
It will cycle - ie has symmetrical on and off times ranging from seconds to hours and runs off 12v.
http://www.rapidonline.com/netalogue/specs/48-0780.pdf
http://www.rapidonline.com/Electron...-function-plug-in-timer-module/61787/kw/timer
It will cycle - ie has symmetrical on and off times ranging from seconds to hours and runs off 12v.
lw395
Well-known member
The fact that the clock motor runs off 230V mostly.
There are two cheap options. If no precise timing is wanted, just a broad control of on and off times, then a 555 timer IC could do the job.
Another solution is to get one of the digital mains plug in timers, these can be modified to run off 12V, although you may have to change the relay which may be 24V internally. The actual clock IC will be internally regulated at some lower voltage like 5 or 3.3. These tend to have a limited number of on/off cycles like 4 per day though.
I suppose whipping one of the segment type (pictured) apart to see how it works might be instructive. If the motor is mains, then you need a low power 50Hz inverter to drive it. Not hard to do depending on precision needed. Either free running oscillator or quartz crystal divided down....
This quickly gets quite involved, so you can see why the NE555 is still with us, despite most professional designers hating it!
A dual monostable gate 74123????? (IIRC!) might be more elegant, giving direct control of on and off times.
Bassplayer
Member
I remember the 555 when it first appeared in the early 70's when I was a bench engineer! I made a bit of dosh then making car wiper delay units.... Still use it for all sorts of stuff. Maplin do a kit for a few quid with a relay that is very usefull.
elton
Well-known member
The Maplin timer kit uses a 555 timer chip, and can be easily modified for automatic repeat. You'd probably need to add a relay as well to power a coolbox.
andy59
Well-known member
you could try this if you can use a soldering iron .http://www.reuk.co.uk/Convert-Thermostat-to-12v-Timer-Switch.htm
ianj99
Active member
The cmos 7555 is a better version.
If connected as an astable (ie an oscillator) with a frequency of about 12 pulses per hour, the duty cycle can be adjusted to vary the coolbox on time from 0 - ie off, to 100% ie on all the time at the turn of a knob.
So for exampe, you could turn it down overnight, and up high on a warmer day thus giving greater flexibility than a fixed timer.
peteK
Well-known member
Lots of 12v timers out there but I want one to control a coolbox running 15 minutes on, 30 minutes off. Something like this but 12v.
Any ideas?
Wanted something similar myself to reduce current consumption on a coolbox and found that a central heating timer/thermostat would possible work.The type that take 2AA batteries,have yet to put the idea in to practise.
elton
Well-known member
How? Do you mean it stops changing state? Or do you mean it will have a very brief on state?
ianj99
Active member
I was exaggerating to make a point!
In fact with a 555 10-90%* off v on or vice versa depending on the circuit, is more realistic.
If you used a switched pot then either 0 or 100% becomes possible when the switch is open (for example by putting the switch in series with the timing cap)
(* eg you could vary the on time from 1min on, 9mins off, to 9mins on, 1min off)
emnick
Member
Timer
Most intruder alarm suppliers provide small 12v timers. They are normally adjustable from a few second to an hour, come with relay (C/NO/NC) and adjuter on a small circuit board.
http://www.tk-consultants.co.uk/ I have used for many reasons and keep one on the boat for use.
Most intruder alarm suppliers provide small 12v timers. They are normally adjustable from a few second to an hour, come with relay (C/NO/NC) and adjuter on a small circuit board.
http://www.tk-consultants.co.uk/ I have used for many reasons and keep one on the boat for use.
pampas
New member
Yes they do exhist. www.cpc.co.uk sell pc timers , I did what you want to do, works a treat but you will need to buy/make a box and a bit of time to adjust to your needs.
tjmobile
New member
As mentioned earlier in the tread, I would send REUK an email neil@reuk.co.uk. Neil will make a bit of bespoke circuitry to do exactly what you want for a few pounds, I've used him several times and he's good.
RAI
Well-known member
Colvic Watson
Well-known member
That's exactly it - any idea if they sell in the UK, I couldn't find a UK page?
