Mat's BX Blog

Post by **mat_fenwick** » Mon Feb 06, 2012 1:23 pm

So far so good, but only tested it up to 800w load. The transistors in question are on the output side so will 'only' see about 5A current. They're rated for 10A @ 400V, so should be OK for continuous use, well, as continuous as it's likely to be from a 12V battery!

Mike E (uk) · Post by **Mike E (uk)** » Mon Feb 06, 2012 11:47 pm

Some other semiconductors are switching the input current then.

I was thinking of the dissipation at those big currents and the heatsinking required as the whole assembly looks quite small.

But modern power devices can be very efficient.

or is it fan cooled?

Mike

Post by **mat_fenwick** » Tue Feb 07, 2012 12:02 am

It is fan cooled, but the fan only operates when the output power consumed is over maybe 150w. I guess that is to improve overall efficiency for small outputs. I don't really understand how it works TBH - there are 4 sets of transformer windings fairly close to the input end of the circuit, but what changes the DC to (some approximation of) an AC signal to feed the transformers? The output signal is a fairly square wave, with an off period inbetween positive and negative peaks.

The transistors are all clamped to the case (but need to be electrically isolated as I found out when I at first just used thermal grease - triggered the short circuit protection!) The case doesn't seem to get excessively warm, but not run it at high load for long periods.

Post by **mat_fenwick** » Thu Feb 09, 2012 4:22 pm

What is it with people and being overtaken? There aren't that many overtaking opportunities in the hills, so if I'm stuck behind someone and there is a safe chance to get past then I will - what gets me is the seeming resentment at being overtaken, and refusing to dip their lights. If I flash my rear foglights at them they don't do anything, so it can't be that they have forgotten!

Fortunately I have this (a Hella worklight) on the back, so a quick burst of that soon makes then see sense.

Dollywobbler · Post by **Dollywobbler** » Thu Feb 09, 2012 5:13 pm

It's quite funny when I'm driving the minibuses with a load of old ladies on board. Every time someone overtakes us (which happens quite a lot - I do stick to the 50mph maximum I'm allowed on single-carriageway) there are tuts of derision! If only the saw the way I drive normally...

I doubt flashing your foglights would be even slightly noticable to be honest. BX estate fog lights are piss poor and just look like brake lights anyway. They certainly don't strip retinas like some fog lights do.

Philip Chidlow · Post by **Philip Chidlow** » Thu Feb 09, 2012 6:04 pm

But I bet that Hella knackers their night vision

Mike E (uk) · Post by **Mike E (uk)** » Thu Feb 09, 2012 7:52 pm

I find many drivers have completely lost the ability to overtake anything beyond a bicycle.

When stuck behind the Rover 25 doing 40mph in a 60, they just follow it along like a sheep.

Mike

MULLEY · Post by **MULLEY** » Thu Feb 09, 2012 11:27 pm

I regularly overtake slow buxxers in my TXD

I know, my old slow n/a diesel. I've also noticed that over the last couple of years that speed limits on various roads near to me have been reduced, so instead of being able to do 40, you have to do 30 & 60 roads are now 50. This wouldn't annoy me too much, except now all these same idiots that never even went to the speed limit when they were higher, are doing the exact same thing with the lower speed limits

Yes, some deliberatly decide to speed up, fuxxing dangerous, i just indicate to show that i'm pulling back in & cut them up, they soon get the msg that i'm not taking any of their idiocy. They of course then decide to tailgate, so i just let them get on with it & ignore them, they never overtake though

Rant over

Post by **mat_fenwick** » Thu Feb 09, 2012 11:34 pm

Dollywobbler wrote:I doubt flashing your foglights would be even slightly noticable to be honest.

True, but if someone approaches you from behind, it's a fair bet they are going to overtake when it becomes clear, and me moving alongside (not exactly whizzing past!) should give them ample warning for them to dip their lights.
I don't really want to 'retaliate' against anyone, but I find main beam behind me very distracting, even if tilting the interior mirror. I suppose a fog light that's not part of the main cluster might attract their attention more, but sometimes I really do despair.

electrokid · Post by **electrokid** » Sat Feb 11, 2012 10:23 pm

They're rated for 10A @ 400V,

Normally at 25°C then, depending on the structure / manufacturer, linearly derated to 0A at either 150 or 200°C. So at the sort of temperatures it's going to run at on full load it'll be down to around 5A per device max.

Good to see it's working again

Post by **mat_fenwick** » Sun Feb 12, 2012 11:52 pm

And the next thing to fail is the hard drive on my laptop

Clicked on a Youtube video, everything locked up and I then got a "Windows has been shut down to protect your computer" message on a nice blue screen. Then wouldn't boot at all, and when adding the drive to another machine it wasn't recognised.

Fortunately I'd backed it up the day before (I try and do it every few weeks), and managed to find an old 5Gb drive to temporarily get me going again. It's bizarre that 5Gb is just about enough for an OS and a few applications!

Can't find anything smaller than 160Gb now, I'll never fill all that...

In other news, people keep bringing me things for me to mend! Today it has been an electric drill (now fixed

) and I've got someone wanting the heater motor sorted on their Focus. The garage has quoted for a full dashboard out job, which they can't afford but a quick bit of research suggests you can leave the dash in.

I'm half thinking of trying to make a job of it, if I can put the word out a bit more than to just our immediate neighbours I might be able to bring in a bit of money and give up the 9 to 6 job. Mobile mechanic and general handyman perhaps?

Post by **Defender110** » Mon Feb 13, 2012 12:39 am

mat_fenwick wrote:I'm half thinking of trying to make a job of it, if I can put the word out a bit more than to just our immediate neighbours I might be able to bring in a bit of money and give up the 9 to 6 job. Mobile mechanic and general handyman perhaps?

You'll find they are less inclined to bring you things once you start charging them the sort of money you need to actually make a living out of doing it!

p.s. I'm still pondering on the Kenlow Hotstart, I don't actually use it anymore and can't envisage a need for it now I have a large garage / workshop but it is like new and I need to make sure in my head that I won't need it again in the future before letting it go.

Post by **mat_fenwick** » Mon Feb 13, 2012 9:27 am

Defender110 wrote: You'll find they are less inclined to bring you things once you start charging them the sort of money you need to actually make a living out of doing it!

You're probably right! At the moment I don't actually ask for any payment, but people always insist on something. Sometimes it's favours for favours which can work well, but not to make a living from. I think it would really depend on Lana's job security before I could make any decisions.

Mike E (uk) · Post by **Mike E (uk)** » Tue Feb 14, 2012 6:47 pm

I used to fix a few things for people at work, but fortunately most electrical thingys are now so cheap that people just buy new.

Being a mobile mechanic is a hard way to earn a living, especially in the winter.

Household repairs are becoming more limited because of the legislation regarding electrical wiring etc, but that is still a viable career.

Everyone I know who is self employed, gets almost no holiday and works very long hours.

Mike

Dollywobbler · Post by **Dollywobbler** » Tue Feb 14, 2012 7:06 pm

Mike E (uk) wrote: Being a mobile mechanic is a hard way to earn a living, especially in the winter.

Yes but this is Mat we're on about. He seems to really enjoy working on cars while there is ice forming on them! Strange lad...

...though I'm very grateful!