Basic problem with transistors

[Hero999]

You haven't looked very hard then.

Both RS and Farnell sell them

A minimum order quantity of 5 which will cost you £4.20 for the lot and nothing in postage.
Zetex | Semiconductors | Discretes | Bipolar Transistors | NPN Small Signal
ZETEX|ZTX690B|TRANSISTOR, NPN, E-LINE | Farnell United Kingdom

They might sell cheaper high gain transistors, I haven't looked.

 

[giftiger_wunsch]

You haven't looked very hard then.

That's strange... I searched RS Electronics for the specific product code, and when that drew a blank I searched for 'High Gain PNP' and didn't see any relevant results Edit: Oops misread the schematic, the NPNs are meant to be the high-gain ones, not the PNP

Thanks for the links, anyway. I'll compare the prices.

 

[Hero999]

I'd recommend the BC64 for Tr5 and TRr6 (total cost of £1.18 for 5, from RS) and the ZTX690B (see my previous post) for Tr3 and Tr4.

NXP | Semiconductors | Discretes | Bipolar Transistors | PNP Small Signal

For the diode I'd recommend the BAT43, £4.23 for a pack of 10.

STMicroelectronics | Semiconductors | Discretes | Rectifier | Small Signal Diodes

I've avoided SMT components but if you don't mind soldering, they're cheaper.

I know buying multi-packs might seem like a pain but it'll build up your inventory.

https://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=1124769

 

[giftiger_wunsch]

I know buying multi-packs might seem like a pain but it'll build up your inventory.

My main problem will probably be persuading my tight-ass friend to part with his half of the money. It took me a good half hour to provide him to get himself a set of resistors and provide half of the requires resistors, rather than force me to part with *all* of my 100, 1k, and 10k resistors

Anyway, thanks for all the help. I'll be glad to get the theory behind me and start doing the practical testing. Time to draw up a full set of schematics and plan the layout on my tripad board, then I can test one H-Bridge with a breadboard and finally get the mounting + soldering to tripad board sorted.

I have even less experience with soldering than with electronics theory, so I can only hope that I'll be able solder all of these transistors without destroying them from the heat by taking too long. I'm planning on using a crocodile clip as a simple heatsink though, so with any luck I'll still have 20 working transistors by the time they're all soldered on

 

[Hero999]

Resistors are cheap, as long as you don't buy from Maplin.
You can buy all the resistors you need for this h-bridge for just 41p. Don't bother with the more expensive metal film, 5% carbon film will do.
100R carbon film
1k carbon film
10k carbon film

The total cost of components comes to just over £10 which I don't think is expensive.

If you go to Rapid they're cheaper (½p per resistor excluding VAT) but you have to buy in multiples of 100 and pay for postage, unless you spend >£30.
**broken link removed**

Don't worry about overheating the transistors; you'll have to be a pretty bad solder to do that.

Use a temperature controlled iron, or if you can't afford that, buy a cheap lamp dimmer and use that. Beware, you need to make sure the iron wattage is greater than the dimmer's minimum (normally about 40W). Clean the PCB before you start soldering, tinning the component pads might also be a good idea (I never bother though) and make sure you heat both the component lead and PCB before applying solder. For transistors, solder the middle leg first, straighten the component up, then solder the other legs. Plenty of good soldering tutorials can be found on Goolge.

 

[giftiger_wunsch]

Use a temperature controlled iron

I quickly discovered after buying maplin's cheapest, most puny soldering iron (it was 12W and had a useless tip) that it wasn't going to be much good. I have a 50W solder station with a thermostat now, so that should be up to the job as long as I am

 

[Hero999]

Did you buy that from Maplin too?

Beware, some Maplin temperature controlled irons are just lamp dimmer circuits. I have a cheap Maplin lamp dimmer controlled iron, it's not that bad but I'd rather have a real thermostatically controlled iron any day.

I forgot earlier that you're building five h-bridges which takes the total budget for all the components to £15.40 which still isn't bad in my opinion.

 

[giftiger_wunsch]

I have a cheap Maplin lamp dimmer controlled iron, it's not that bad but I'd rather have a real thermostatically controlled iron any day.

It was indeed from Maplin; what's the difference between the two types?

 

[Hero999]

A lamp dimmer controlled iron uses a phase controller which doesn't have any feedback so adjusting the control just alters the voltage delivered to the element.

A thermostatically controlled iron has a temperature sensor inside the element so if it's too cold, the element turns on, if it's too hot, it turns off.

A thermostatically controlled iron is always better because the temperature is regulated so the control won't need adjusting when soldering large connections which require more heat energy.

Is this the soldering iron you bought?
**broken link removed**

If the answer is yes, it's a cheap phase controlled iron, not a proper thermostatically controlled iron. You could have saved yourself some money by buying a 50W iron and connecting it to a lamp dimmer. I have one of these irons and it's not too bad but I did feel a bit ripped off.

 

[giftiger_wunsch]

Is this the soldering iron you bought?

That's the one. Well at least it's an improvement from the previous one I suppose

 

[giftiger_wunsch]

So much for a total budget of £15.40... total of all components was just over £13 and got put up to over £21 once the delivery and VAT was added. It didn't even mention that it was excluding VAT or that it would charge me £5 for delivery until after it forced me to register, provide card details, address, and telephone number, and according to their terms and conditions, agree to be contacted about offers.

Frankly I am starting to think that electronics distributors are the most annoying people I've ever seen >_> I'll have to get the components from RS this time but if maplin is the only site which doesn't use sneaky tricks like that then I think I'll just be sticking to that.

 

[Hero999]

RS Components give free delivery.

The price of £15.40 I quoted included the VAT.

 

[giftiger_wunsch]

RS Components give free delivery.

The price of £15.40 I quoted included the VAT.

They wanted to charge me £5 for delivery... and the other options were guaranteed next day delivery so I'd imagine they'll be more. Edit: In fact, the delivery cost goes up to £15 or £20 respectively for the other two options.

 

[Hero999]

I've not done an RS order for awhile, may be they've changed it since.

What about Rapid? Are they any cheaper?

 

[giftiger_wunsch]

What about Rapid? Are they any cheaper?

Probably about the same, they charge the same amount for delivery. Maybe there's a threshold for free delivery with RS; I'm sure I can think of some other components I may need in future.

 

[giftiger_wunsch]

Sorry to be a pain, but for the parallel port connections on my board, I'm planning on soldering a header onto the board for which I can get cheap connectors to make it easy to change over wires on the board; but I haven't been able to find a suitable component to do this.

The board has a rectangular array of 50 parallel bit terminals separated 2.5mm apart and arranged in two rows of 25 (the holes have a diameter of 1mm). Rapid seems to do a very cheap single-row header which can be cut to a desired length, but the spacing is 2mm and I don't seem to be able to find a 2.5mm variety. Also seems to be designed for board-to-board so I don't know about connectors.

Thanks in advance for any help

 

[Hero999]

I think I've figured it out: you need to open an account with Rs in order to get free delivery.

EDIT:
I don't know much about the connectors, I'll look into it.

 

[giftiger_wunsch]

I think I've figured it out: you need to open an account with Rs in order to get free delivery.

They forced me to create an account in order to be able to place an order at all. They even made me provide company details when I'm not ordering on behalf of a company anyway.

Edit: I just read the same thing you said from their website... Perhaps by 'account holder' they mean something else

Edit again:

I don't know much about the connectors, I'll look into it.

Thanks; sorry to be a pain but I tried searching for myself and didn't see anything suitable; I don't have enough experience with electronics to be able to find something like this. Maybe I should ask in the Datasheet / Part Request forum.

 

[Hero999]

What about an IDC connector?

These are 26 way, just leave one of the connections unused.

Socket (cable mount):
26 way IDC socket

Plug (PCB mount):
26 way IDC plug

You could use a header rather than the PCB mount plug, if you want to be cheap, but it offers no protection against reverse polarity so I wouldn't recommend it.

 

[giftiger_wunsch]

Hmm I don't know, the IDC sockets don't seem to specify how far apart the pins are, and would make it more difficult to have only a limited number of pins in use, or to have several different devices connected to different groups of pins. I was planning on using a header like **broken link removed** but they're listed as PCB interconnects so I don't know if they could instead connect the PCB to wires using suitable connectors. Though the link I posted is 2mm and I need 2.5mm, which I don't seem to be able to find. Figures the rabbit prototyping board is being incompatible with everything else again >_<