Recent content by moorea21

I'll probably stick with splicing into the standby 5V line, as my PC has no side cover, so the 'guts' are exposed anyway. I originally did this for extra cooling when video editing; I don't do that any more, but the lack of a side panel doesn't seem to be a problem, apart from visually.

The self oscillating piezo ideas sound good (there's that pun again...) but I'm hoping to build with what I have lying around, which doesn't include self oscillating piezos, although I have 2 non self oscillating ones glued to the bottom of a small tin, so they'll do fine I think. The minimal...

Many replies! Thanks to all of you. Hippy:- I didn't know it was possible to tap into a 5V supply from a PC that's plugged in but not switched on. Previously when I wanted a loud piezo, I used 2 of them, didn't know I could overdrive one. All sound advice. Pun partly intended. My PSU...

I'm hopefully going to put together a picaxe based 'alarm', which will sound when/if I leave the power switched on at the wall when I've turned the PC off. Leaving it like this wastes electricity, as the monitor etc are still on standby, and I keep forgetting... Powered from a 5V phone charger...

I have a pile of old heat sinks somewhere, and plenty of fans. I had expected to need to use some sort of forced cooling, otherwise the power capabilities of that tiny chip start to look even more insane than they actually are,

That's great, thanks for taking the time to find that, I had no idea you could get an H bridge on an IC that would handle anything like that amount of power; it wouldn't have occurred to me to look for one. I certainly wouldn't have wanted to build one from scratch if at alI possible. I've...

Hi PhilHornby, I'm using the controller that came with the motor, it outputs the 230V DC, and yes, the motor reverses when the contacts are reversed. Speed is altered via a pot (native to the controller,) which I'll replace with a smoothed picaxe pwm signal. I haven't built that yet, but have...

Thanks Aries. So it would be slightly beyond inconvenient, and maybe lead to a dead power supply. E-stop switches on the limits of the screwjack would disable the motor's power supply when it gets to the end of its travel, so a rougue motor wrecking things should be avoidable. Another idea I've...

Hi premelec, I have noticed that relays rated for high current AC are rated for much lower power DC, which actually suggests the reverve of what you have mentioned, so I'm confused now! Also, what would be the advantage of switching off the AC end of the power supply? Hemi345: I have so little...

Yes, I wonder if it only ships with its controller/power supply, which is for 50/60Hz. Google didn't help today. Maybe tomorrow...

Thanks Aries, that looks like the best option for current and cost. I'm not sure how they would be connected to emulate an spdt and a dpdt as in hipyy's diagram? Also, I've just noticed in Hippy's original reply : moorea21 said: I have a treadmill motor (rated 1.5Hp, 4800...

So in view of the fact that I'm unlikely to be able to get the full specs for the motor, including things like start up current (is that the same as in-rush current?) it may be necessary to use a factor of safety of, say, 2, when specifying the relays, ie 10A? And maybe have a 'ramp up' of motor...

I would think it would still work without the relay on the left? The voltage across the motor when it isn't turning should be 0V, so its the same as having the on/off relay? Would 230DC 8A be sufficient for the dpdt? Thanks Hippy

Thanks both, I originally wanted to use spdt's as I already have some, but they have 12V coils and are 240V 10A, which I started to think were not really substantial enough(?), I could use a 5v coil dpdt instead. I'll look for something similar to the RelPol one in the UK; suggestions for a...

Hi, I have a treadmill motor (rated 1.5Hp, 4800 rpm, 230V DC) and controller which I can run from a picaxe pwm. The controller only runs in one direction, but I want to use it in reverse too. In my intended application, it will always stop for at least a fraction of a second before reversing...