Langstone build thread - join in the fun!

[g4eml]

Hi John,

I use one of the XL4015 converters in mine. Seems to work OK but does run quite hot.

Colin.

[radiogareth]

ALthough I haven't used this exact module yet (running off a mains 5v 5 amp unit culled from soemething) I have used similar SMPSU modules where the 'tab' has either been left off or cropped. I soldered on a 16g copper L shaped tab and bolted that to the side of the diecast box. OK it got is 'ass roasted' when I soldered it but it runs cool now....
Gareth

[i2NDT]

just found this video about the XL4015:
https://www.youtube.com/watch?v=8cRmGNmqRYc
go to minute 29:40 to see how it behaves (and heats) with 12V in, 5V out and 2A to 3A load...
unfortunately he doesn't measure the output ripple and/or noise (the switching frequency should be 180 KHz).

Claudio

[G7JTT]

Thanks for the replies, video does seem to suggest around 3A is ok at 5v from a 12v supply, but it will get hot ! Think I'll try Gareth's idea and see if I can create a heatsink and bolt it to the side of the case. It does have a stick on heatsink but never really thing they transfer hear that well.

On another note why is it, that the leads, switches, connectors etc always seem to be the most costly part of any build ? Needed some 8mm 2.5mm standoffs ended up paying over £3 for 10 ! Really need some more old junk ex equipment to strip down for cheap parts, stroll on when rallies start up again

Cheers John

[i2NDT]

ok for the temperature, but I was more concerned about the output voltage drop at load...

Claudio

[g4eml]

The quality of the inductors used in these boards makes a big difference. I have one board that gets extremely hot at 5V 2A and one that just gets warm. The only obvious difference is the hot one uses a surface mount enclosed inductor, the cooler one uses a wound toroid. I suspect some manufacturers are saving money on this component at the expense of performance.

[radiogareth]

Spurred on by Jims article in CQ-TV about the small eBay 70cms amplifier, I bought one too. Seems close enough to identical.
As I would generally be using it portable, I wanted a stable bias voltage, so didn't use the input supply as that could be all over the place. Instead I tapped off the on-board 5 volt regulator via a multi-turn pot. My unit didn’t draw the same amps as Jims, but it did deliver a very handy 11 watts or so, with a bit less for DATV use. As it had no output filtering, I wondered if one of the cheap low pass filters from eBay might survive. Testing one showed it got slightly warm but no visible duress shown(i.e. no magic smoke) so I cut off the input SMA, used a decent silver mica coupling capacitor (the one fitted was a tiny 200pF ceramic) and removed solder resist as required to solder it down to the motherboard (LHS) and solder tabs under existing screws (RHS). A handy little unit to go lightweight /P with (DATV SOTA??) or to use with the Langstone.

Gareth

2020-06-16 15.32.29.jpg (82.78 KiB) Viewed 4736 times

[G4FKK]

My trusty Langstone/Portsdown (LangsDown?), getting closer to having its lid fitted. With RadioGareth 3D printed panels and an Arduino Micro impersonating a mouse, monitoring/switching stuff and interfacing with a Nextion display...

I've also managed to GPS lock a 40MHz oscillator for the Pluto (not installed yet), and get an EPS32-CAM board working which may be fun with the Portsdown in due course. This lock-down business is certainly helping me knock a few items off the Project List

[G7JTT]

Just a word of warning if your using a XL4015 module the tab is at positive potential at what ever the output voltage is ! So make sure it's insulated if bolting it to a metal box/heatsink

Getting there slowly John

[radiogareth]

Just bought this rather nice 7 way switch for $75 (he accepted my offer of $75) + shipping. Data is here with power handling on the first few pages then the many variants:https://www.ducommun.com/pdf/RFCoaxialS ... 120215.pdf
https://www.ebay.co.uk/itm/SP7T-DC-6GHZ ... 2749.l2649
Its actually for remote switching down my garden rather than my Langstone, but if you are building a 7 band go-box you might like one too. Hes got loads of nice stuff listed and is clearly amenable to a deal.
Gareth