Stepping up voltage

[Dermotx]

Hi,

I have a 1.2v output from a separate timer which I want to connect to leg 4 of a picaxe 08 chip. I need at least 2v to get a logical 1.
I can use an op amp to step up the voltage but it means an extra chip and two extra resistors.
I also have a 3v supply in the circuit which would be ideal if i could connect it to leg 4 using a transistor or a mosfet using the 1.2v output of the timer to the base of the transistor. The problem is leg 4 doesn't seem to draw any current so this won't work.
Any ideas or is the op amp the best solution?

Thanks
Dermot

 

[Michael 2727]

Instead of using the input as a digital input e.g high / low.
Try using it as an ADC and select the correct
value you need to perform the switching task.

Opps using 08 not 08M, you will have to
use leg6/input1.
It's too early, coffee hasn't kicked in yet
I may get better as the day goes on,,~ ;o)


Edited by - Michael 2727 on 03/06/2006 00:17:56

 

[Dermotx]

Thanks Michael, that's a great idea.

Regards
Dermot

 

[hippy]

Depending on what your 'timer' is, you may be able to get the voltage adjusted by running that and the PICAXE off 'virtual power rails' ...<code><pre><font size=2 face='Courier'>-----.------------------.-----
_|_ |
_\ /_ |
| .----^----.
.----^----. | |
| | | |
| |&lt;-------| |
| | | |
| | `----.----'
`----.----' _|_
| _\ /_
| |
-----^------------------^----- </font></pre></code>

 

[Dermotx]

Thanks for that suggestion hippy but unfortunately the timer is powered by a 1.2 v supply. It's an ordinary mains plug in socket timer but I have stripped away everything except the timer part. If I try to increase the voltage everything on the LCD display lights up so I'm stuck with 1.2 volts supply.

Regfards
Dermot

 

[manuka]

I take it the timer is running off a 1.2V NiCd/NiMH cell? Consider using the innards from a el cheapo solar garden lamp (selling here in NZ for ~&#163;1 !). These provide ~4V spikes @ ~10mA for the white LED, which smooth via a suitable electrolytic nicely- we've even driven an entire low duty cycle 08M/DS18B20/433 Tx setup off one.

 

[hippy]

This might work, and you could also take the -Ve of the supply to 0V and power with (1.2V+Vdiode)...<code><pre><font size=2 face='Courier'> .-------------.
5v -----. | |
| .----^----. |
.----^----. | | |
| | | | ---^---
| |&lt;-------| | -.- 1.2V
| | | | |
| | `----.----' |
`----.----' | |
| }-------------'
| _|_
| _\ /_
| |
0V -----^------------------^----- </font></pre></code>

Edited by - hippy on 04/06/2006 17:04:22