intermittent sounder

[williamwright]

I need a sounder of some sort that will sound briefly once every few minutes. It's to remind a van driver that he has the inverter turned on.

12V.

[Rod Speed]

williamwright [e-mail] wrote

Even the most basic 555 circuit will do that fine.

[Owain Lastname]

I would suggest that many drivers would 'tune out' such an alarm, unless you fix it as requiring a positive response or the inverter turns itself off after n bleeps.

Owain

[Harry Bloomfield Esq]

I have a 2x AA powered add on temperature alarm, which I use on my freezer. When the alarm is triggered, it gives a couple of bleeps every minute or so, the every minute or so makes it especially difficult to ignore and the noise to stand out. It can be set to trigger on rise or fall in temperature, at any trigger temperature from (I cannot remember precisely) minus30C to plus 100C, with a remotely wired sensor.

I have it set to alarm if the temperature rises above -14C as a warning if the freezer door has been left open, or not closed properly. Freezer is in the util and it can be heard in the kitchen. It cost me around £7 on Ebay.

I'm thinking - fit the temperature sensor on the heatsink of the inverter, and it can be set to trigger by the heat from the inverter.

[Brian Gaff]

Sounds like the ideal job for the old 555 timer chip and one transistor and the sounder of your choice. Brian

[John Rumm]

My approach would probably be a cheap Arduino nano clone (~£5 or less from Ali-express / eBay), and a small speaker or pizzo sounder. That way you can fiddle with the nature of the tone(s) and the timing etc to get the effect you want.

You could just power the arduino from an old phone charger running from the inverter - that way it only powers up and does it's stuff when the inverter is running. So you would not even need to do anything to sense when the inverter is on,

[Clive Arthur]

Use a smoke alarm, but run it from say 5V via a car USB supply instead of its 9V battery. That way, the low battery warning will pip every so often.

[Robin]

ISTM much depends on what (if anything) the van driver listens to while driving: Motorhead e.g. is likely to require a bit more than a smoke alarm's 'beep'.

[Rob Morley]

I don't suppose he'll be using the inverter while driving.

[williamwright]

Yes, that's a big part of it. They charge their tools as they go from one job to the next.

Bill

[charles]

By Ryobi kit has a charger which runs off 12v. Ideal for this task.

[Rob Morley]

Ah, I assumed they'd be running mains kit on the job, not on the road. There should be something neater than 12 VDC to 240 VAC to 18 VDC or whatever it is they actually need to juice the batteries. I suppose there's a lack of interchangeability in the connectors too.

[SH]

there are laptop chargers around that will plug into a cigar socket and provide the required DC voltage...

I have seen some go as 24V at several amps.

So should be fairly easy to make up a DC charger to chare up toll batteries from a suitable laptop in-car charger.

Actually, why not google to see if in-car chargers are available for the battery tools? may be cheaper than an inverter?

The mains chargers can stay at home or workshop and use the in-car chargers in the van?

S.

[SH]

If the input current of the inverter is not too high, what about a split charge relay like that found for caravan tow bar auxiliary electrics (that supplies fridge and supplementary battery?

Connect the inverter to the split charge relay and then when van driver removes keys, cuts the current to the inverrter automatically?

[williamwright]

No. The inverter is powered from a 110Ah aux battery that's charged via a split charge relay. It's important to be able to put tools on charge whether stationary or travelling. Also, there are other reasons for having 240V available in the van.

Bill

[Animal]

that's one way to ensure the thing gets smashed

I'd use a 555, a hex invertor, even a discrete osc circuit or whatever. Presumably the OP doesn't know how to do that.

[John Rumm]

Rather than any continuos tone, I suspect a medical equipment style alarm would be less irritating and more effective.

Intermittent - only every few mins, and designed to be informative rather than annoying - a short note sequence to give a "note message" that is onomatopoeic. e.g. Oxygen warning has three notes to match the syllables of the word, and the typical intonation.

[Harry Bloomfield Esq]

That is what I find too - a continuous beep, beep beep is easy to get used to and eventually ignore, but if there is a sufficiently long gap between the beeps, that you become used to the silence, the beep becomes much more attention grabbing. In which case the beep only needs to be audible, rather than loud.

[Paul]

I would go with an RPi and voice synthesis :-)

There is actually a small chip, which connects to a flash ROM for its voice samples. And for only a couple bucks of material cost, you can have (low quality) voice output. (The chip may have been made by Winbond.)

But with the RPi, you can even change the lecture content, as things come to mind.

"Did you know the inverter was on ? An inverter is a device that wastes electricity."

"To stop these voice messages, turn off the inverter."

"Inverter capacity remaining, now down to 43% "

"The Inverter control is the third knob from the right"

An RPi is a waste of materials, but gives infinite flexibility for making interesting noises. You could easily set a period of ten minutes between voice emissions, without needing dedicated hardware logic chips to do it.

There are probably simpler electronics modules than that, which are a bit easier on electrical consumption. Maybe a Pi Zero would be a reasonable choice from the RPi family. But there are also microcontrollers with lower consumption.

Paul

[alan_m]

My answerphone has an intermittent beep that can get bloody annoying if I don't get off my backside and either listen or delete the message.