Runback Time (SMD) Two hour off delay

[60 oldjohn]

Is there a device that will switch 3V 3Ma off after about 2 hours. Must be no larger than 12mm x 20mm x 4mm H.


TIA, John.

[Herald1360]

Probably.

If you can cope with SMDs, you could build one yourself using a 4060 or similar oscillator/divider chain CMOS chip and a few discrete bits. 50 thou blob board is readily available.

[60 oldjohn]

I was aware of the 4060 and regularly use 0.7mm board to make the PCBs for SMD. My only concern is the 1000uf cap size wise. If I can use the 4060 without a large cap, the 4060 may work, just a shame there is not a ready made chip available.


John.

[Trigon.]

There are chips available but they cost a few pounds, e.g. the LTC6995, which is a 6 pin surface mount device which doesn't require a timing capacitor. (Useful to keep within your 4mm height limit !)

e.g. from the data sheet - a 1 hour auto shutoff timer (which would also need a fet or transistor to invert the output) :



Cheers

[Herald1360]

The 4060 is an oscillator-divider unit, so you can keep the capacitor size down since you can divide the frequency / multiply the period by up to 2exp14.

[60 oldjohn]

Originally Posted by Trigon.

There are chips available but they cost a few pounds, e.g. the LTC6995, which is a 6 pin surface mount device which doesn't require a timing capacitor. (Useful to keep within your 4mm height limit !)

e.g. from the data sheet - a 1 hour auto shutoff timer (which would also need a fet or transistor to invert the output) :

Attachment 191708

Cheers

Thank you Chris, but I think the LTC chip type is the chip to try, or I wonder if there is a similar chip that did not need the output inverting. The PCB may have to be 12mm X 12mm x 4mm H which would be possible using LTC6995.


John.

[Trigon.]

Originally Posted by 60 oldjohn

I wonder if there is a similar chip that did not need the output inverting.

The output polarity on the 6995 can be selected via the DIV input, but then the oscillator has to be stopped by a different method, possibly by feeding the output back to the reset.

Everything depends on how the timer is to be started and whether the timer itself is to be powered down at the end of the timeout.

Cheers

[60 oldjohn]

Circuit uses 3v 3ma powered from 3v lithium battery. I need to press the switch to turn circuit on, then after 2 hours switch off, no power at all to be consumed. The LTC chip sounds great if I can get it to work as stated above.


John.

[Trigon.]

So something like this ?:-



Cheers

[60 oldjohn]

Originally Posted by Trigon.

So something like this ?:-

Attachment 191744

Cheers

Thank you for taking the time to draw the circuit, The two components with thee legs, Is one a N channel Mosfet ? and the other a P channel MosFet ?


Anyone know where I can buy the LTC 6995-1 ?


John.

[Trigon.]

Originally Posted by 60 oldjohn

Is one a N channel Mosfet ? and the other a P channel MosFet ?

Indeed yes, nothing special. Just a first stab.

Originally Posted by 60 oldjohn

Anyone know where I can buy the LTC 6995-1 ?

They do seem to be rare in the UK. Rapid appear to have 'discontinued' (?) the whole range. Mouser.uk and Digikey.uk list them at over £3 ea. but they're delivered from the US and the p&p would be £12 or so (for orders under £33).

I eventually did find them in the UK at Anglia Live (an approved distributor). They're actually a bit cheaper, but again handling makes it £8.13 for one off, then £2.20 for each additional one.

http://www.anglia-live.com/products/...N-lTC6995iS6-1

Cheers

[Vintage_RC]

I would do it with an 8 pin PIC, probably need a delay loop within a delay loop because of the long period.

[Trigon.]

Originally Posted by Vintage_RC

I would do it with an 8 pin PIC, probably need a delay loop within a delay loop because of the long period.

If it were me I'd use a 6 pin PIC. What do you need those all those extra pins for?

Cheers

[60 oldjohn]

I will give Rapid Electronics a call on Monday in case they can help. The price quoted is a bit steep, for an item that could be £2.20.
Alan, a PIC may be the easiest but the programing is beyond me. I have a friend who might be able to help, another avenue to explore.


John.

[MikeM100]

Multifunction Delay Trigger Timing Chip Module Timing 2s - 1000h Timer IC F

eBay item: 292215199121 may do exactly what you want to do !

[Cobaltblue]

Thread reopened at OP's request.

Cheers

Mike T

[60 oldjohn]

Thanks Mike T, I have only just seen MikeM100 reply, I think it is this https://www.ebay.co.uk/itm/272581042....c101111.m2109 C005 Multifunction Delay Triger Timer. The board is 12mm x 12mm x 2mm. Available for around 40p each. The link shows pads P1 and P2 these are needed to set a time of more than a few minutes, make sure what you order has these. For ~ two hours I linked p2 and used a 390k resistor. You tube has this video about the C005. https://www.youtube.com/watch?v=C4C2H_3BU3o The timer can be set from 2 seconds to nearly 6 weeks!

John.