I’m on the hunt for a new multi-meter. I’ve got several already, ranging from cheap and cheerful that I leave in the boot of the car for emergencies, to small, portable with additional features for environment monitoring like temperature and sound levels that I carry around in my rucksack, and some more typical larger units for workshop use. The other day on a whim, I got them all together and decided to see how accurate they were. I set my PSU to 12v DC, and one by one used each one to measure the measure the output voltage. I started with my Thurlby Tandor bench multi-meter and left that one connected thought the test to monitor the output of the PSU in case it started to drift.
Every meter gave slightly different reading. They weren’t out by much, but it did get my thinking that it was time I invested in a reasonable quality one that was calibrated for bench use.
So, I went to EBay initially to have a hunt around to see what new equipment was available. I stumbled across a make I’m not familiar with, Uni-Trend. I’ve been seeing a lot of their equipment around recently and I found a rather nice unit – UT803 available in the UK for 104.95 GBP including VAT and delivery. On further inspection I found that it’s actually being sold by Rapid Electronics; this is why the make seemed familiar as I’d probably seen it on their site previously.
Annoyingly, the UT803 is listed on the Rapid main site, but it costs 114.07 GPB including VAT and you’d get free delivery on that order as it’s over £30.
The Fluke 5211 from Rapid’s site is £246, but their Ebay shop sells it for £279.
I was displeased to see many other differing prices for Rapids offerings.
They have some 3.3v MES bulbs that are 100% more expensive on Ebay, but some hand tools that are cheaper, and the discrepancies go on and on.
MPLAB ICD2 Ebay - £154.95, Main shop - £150.50
Pack of 100 resistors - Ebay £0.99 - Mian shop - £0.62
The ST Mems Sensor Evaluation Kit (82-1004) which is 79.50 on Rapid’s site, is only £38.99 from their Ebay shop.
You’ve really got to check both places now if your after the best prices from them. Also, delivery charges for orders under £30 from their main site attract a £5 + VAT delivery charge. The charges from their Ebay shops are much more reasonable.
If you find an item in their Ebay shop your intersted in, at the end of the product description is a numeric code. Just enter this code into the search on their main site and it will find the same product for you making it faster to do the price comparisons.
Wire strippers that is... sorry chaps...
Good tools are expensive and a decent pair of wire strippers can set you back a kings ransom, and by decent I mean a pair that you can use with one hand, will just grab the end of the cable and strip without too much pre-adjustment, not damage the metal inner conductor, and work pretty much every time.
If you want to find out just how much a pair can cost, checkout some of the bigger suppliers like RS and Farnell.
Well, all is not bad news. Rapid Electronics
have some Abeco Micro Strippers on offer (Part number 86-0325) for less than £20 including VAT. I’ve had an identical pair of these for a while now (and paid a heck of a lot more for them at the time) and they are perfect for Hobby Electronics. They are a little bit smaller than the standard full size pairs which makes them ideal for use in tight spaces. They will happily work with common 10/0.1 stranded hook up cable and the 1/0.6 solid core preferred by breadboard users. They will of course also work with larger gauge wire as well.
They are supplied in a little plastic case, with three pairs of gripping pads and a small adjustment screw-driver.
I would suggest if you don’t have a decent pair or wire strippers (or your just looking for a second pair), whilst they are available at this bargain price you invest. My larger pair that I’ve used almost every day for 15+ years are still going strong.
Here’s the technical blurb:
· Self adjusting over the full range
· Small enough for closely packed assemblies
· One hand operation allows use over long periods without discomfort
· Incorporates a cutter which will cut wires up to a maximum of 1.5mm²
· Supplied with three pairs of differently serrated gripping pads to suit various insulation materials without damage
· Replacement jaws available
· Weight 76g
· Dimensions 155 x 80 x 14mmhttp://www.rapidonline.com/Tools-Equipment/Microstrip-self-adjusting-wire-stripper-30552
Now I’m not in any way connected with Rapid Electronics in the UK,
but I really do like using their services. If you order before around 8pm they usually deliver next day, and whilst I do wish their product range was a little larger in some areas, you can usually find what you need (or often an acceptable equivalent) and their prices are usually some of the best. As always when shopping, it pays to look around of course.
You can also be sure that their stock is genuine and non of this fake or out of spec rubbish that you can sometimes get landed with off auction sites.
I’ve just been looking on their site this morning, putting together my next order and they have some real bargains right now. I’ve listed a few below that caught my eye.
47-3302 L78S05CV +5v 2amp regulators at 20p each (normally they are 56p)
You can use these as a direct replacement for the usually cheaper 1 amp versions.
78-0206 16 key waterproof keypads at 3.15 each.
Just because it’s waterproof doesn’t stop you using it indoors.
22-2431 15-way 90 degree pin headers (like molex connectors) for around 7p each, and 22-2432 16-way versions for 11p each. These are ideal for cannibalising for their 90degree pins. You can then use these pins to convert smaller way connectors into 90degree versions. This means you don't need to buy seperate striaght and the more expensive 90 degree variants. The 16 way ones are also great for soldering to LCD displays as well.
77-0142 26-way right angle PCB mount hi-density D-type plugs. These are great for those projects that need a nice compact hi-density connector on the front. And they are only around 2p each.
They also have loads of stuff in their clearance section that’s worth a search.
I’ve blogged about wire cutters previously and why I only ever buy cheap pairs. Old pairs are often kept as they always come in handy for silly jobs.
At the weekend I used an old pair to try and break into some plastic gizmo; I didn’t really care on the damage to the thing… I just wanted to see what was inside.
I've done some silly things in my time, but I've never had a pair of cutters split like this on me.
Because a lot of people have asked me about PIC programming using the AMICUS18 BASIC compiler and how to do things, I thought it would be interesting and useful if I wrote a series of articles on the subject (see here).
So, to kick things off I’ve placed the first three on this website. I’ve never done anything like this before so please let me know what you think or if there are any topics you would specifically like me to cover.
I’ll be adding more parts on an on-going basis.
You can find the dedicated page here:
I've added a new construction project for a plug-in PCB module for breadboards
It allows one of those cheap and nasty plug-in mains transformer type PSU to be used as the power source for a +5v regulated PSU thats suitable for powering PIC, TTL/CMOS logic and other circuits.
Because there's no direct electrical connection to the mains, it's perfectly safe for beginners to create. You can also throw one of these together for less than £2.00
If anybody in the UK is interested, I've got a couple of blank, etched and drilled PCBs that I'll give away on a first come, first served bases. All I ask is for £1.00 to cover my postage and packing costs. All you need to find are the 13 components to assemble the thing.
Plug-in Breadboard regulated +5v PSU
Been really busy over the last few days with a lot going on.
I’ve started writing a series of articles on programming PICs with the AMICUS18 PIC BASIC compiler from Crownhill Associates
. Each article covers a specific topic starting with how to get everything configured and writing your first “Hello World” BASIC program, and then onto interfacing to common electronic components. Each article includes circuit diagrams and source code.
I’ve also added a review on a new toy… I mean tool, for the bench; a Weller gas powered soldering iron which recently arrived from Rapid Electronics
Now I love clocks, I really do. They are great projects because you can place them on the mantelpiece or in other prominent locations as a functional working device, partners can’t complain about it being another piece of junk because they do something useful, they come in all sorts of shapes and sizes and are great beginner projects and once you’ve built it, you can tell people “I made that”.
Recently, I’ve been working on a new clock project and it suddenly occurred to me that except for the physical display aspect of the clock, the internals are nearly always the same. A battery-backed RTC for the date/time (usually a Dallas DS1302) with support components, a PSU section of some type that usually puts out 5v for the logic and possible an additional higher voltage for larger LED displays, a PIC to glue everything together and some display driver hardware.
The only really custom part is the physical display, and the PIC firmware, and this got me thinking; “Can I construct a generic clock that can have many different displays connected, and just need to update the PIC firmware as required”?
So, this is what I’m currently working on. Some more thought is required on some of the projects finer attributes but I have an initial prototype sat on my breadboard that’s driving a strange looking LED display with 60 LEDs on it (I’ll post pictures later) and it seems to be working well.
The next part is to design several other display units and make sure that they can be driven by the hardware.
I use a DS18B20 temperature sensor IC in several of my projects and I encountered an interesting problem recently. This IC runs over Maxim’s 1-Wire interface and should, in theory, work over cable lengths of several hundred meters or more.
However, when I tried to run one of these sensors over a cable longer than around 50cm it refused to work. Shortening the cable always brought the sensor back to life.
In desperation I tried a different sensor and hey-presto, it worked on my test 5M cable.
So, I purchased 10 sensors off EBay and gave them a try. Each one worked perfectly on my 5M cable so I can only assume that I’d been unlucky to have a semi-faulty sensory IC.
I’ve binned this IC as whilst they are rather expensive if you buy from a regular supplier, at less than £2 each off EBay, I wasn’t going to risk having the IC suddenly fail on my at some point in the future; and there’s obviously something wrong with it.
At last, it’s completed and this new programmer will make my life so much easier when it comes to PIC development.
This has been one of those projects that in some ways, I wished I’d not started as there seemed no end to it and everything just seemed to go wrong. I blame the fact that I never really had any time to just sit down and do this project from start to finish, but now it’s completed and working, I’m really pleased I stuck with it.
And here it is.
Ok, a bit of explanation as to what this lovely, beautiful piece of equipment can do.
Inside the case are six PCBs packed with electronics. There’s a PCB that contains a PSU with 5v regulator and an adjustable voltage regulator; set to around 7.3v that drives the LEDs in the push switches. Also on this board is a MAX232 and associated electronics that provide two RS232 interfaces; more on these in a second. There are four almost identical boards; one per output channel that contain a 16-bit shift register, driver chips and relays. The final board contains the PIC and driver logic that runs everything.
Also inside are two Microchip PICKIT programmers (a PICKIT2 and a PICKIT3).
On the front panel there are four 9-way D-Type connections that can be used to connect an ICSP cable to a project under development, or, in the case of this new programmer, up to four projects in development; this will make multi-PIC projects a lot simpler to develop and debug.
You can select which PICKIT is connected to which of the four ports and you can of course only connect each programmer to one port at a time. The unit also has in-built support for RS232 which I use for project debugging. My custom ICSP cable has provision for serial data to be set from the PIC to the outside world and this makes it possible to send any debugging information from the PIC, into my programmer which level shifts from TTL to RS232 and then out to a dumb terminal emulator. I’ve made provision for up to two serial ports and again, you can select which serial port is attached to which input. The serial ports are also available via four, 4mm banana sockets on the front panel for use within other projects.
The upshot of this is that you can connect one port to each PIC project under development, and allocate either of the internal programmers / serial ports on the fly to each port as required without the need to keep unplugging cables all the time.
The advantage of this new unit over my now obsolescent one (which only support up to three outputs and was very clunky), is that I could, in theory, expend the design to support as many output ports as required. It would be a lot of additional effort to increase the number of PICKIT programmers that can be supported. This was going to be a six port unit but I didn’t have a case large enough at the time. But now I’ve got all the hardware sorted out, it wouldn’t be too difficult to build a larger one if required. I’d need to tweak the PIC firmware that controls everything of course, but that’s no real hassle.
Oh yes, the reason I've used a PICKIT2 and a PICKIT3 is simple. I prefer the PICKIT2 as it's much faster than the 3, but the 3 supportes a couple of PICs that I've started to use that the 2 dosn't. I could have used any combination of programmers if desired, or even completly different programmers. It's just I rather like the Microchip ones.