How to wire this... - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 20, 2012, 07:43:33 am
content: G'day,I bought this board and a power board that has the same hollow power pins, any ideas on the cables and connectors I should use?http://i.ebayimg.com/t/Power-Transistor-Curve-Tracer-adapter-XY-Oscilloscopes-/00/$(KGrHqIOKjIE26kgwt79BNy934DJfw~~_35.JPGThe 3 hollow pins (+15V G -15V) are at the top right and about 1mm diameter and about 10mm apart, they protrude by about 3.5mm.The PSU has the same hollow pins with AC G AC on one side and +15V G -15V and I bought a cheap AC240V to AC12V transformer with white and grey wires to power that.I am going to put it in a case with an IEC plug going in to the transformer.Thanks.Richard

author: peter.mitchell
author_rank: Super Contributor
timestamp: October 20, 2012, 07:48:13 am
content: Be sure to fuse and earth.

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 20, 2012, 07:59:59 am
content: Thanks Peter for the lightning fast response, the Jindel GET-1003 transformer is in a plastic case and only has 2 wires in and 2 wires out (for halogens usually) so earthing this whole setup would have to miss out the transformer, can you give me tips on how to wire it all?The IEC socket would have an earth pin, so would I wire that to ground on the +/-15v supply and wire ground on the output side of it to ground on the curve tracer?I can use a fused IEC socket so that gives me a fuse.Also did you have a thought about the connectors that fit this hollow pin, I haven't seen it before, is it just meant to be soldered or does a 3-way screw terminal fit it?I posted in the beginners section because I am pretty new to all of this.Richard

author: peter.mitchell
author_rank: Super Contributor
timestamp: October 20, 2012, 08:31:01 am
content: Is the chassis of the case metal? I assume it is. When mounting the transformer to the chassis you should attach the earth to there with a spring washer and a nylock nut, earthing the chassis. Between the active of the IEC socket and the transformer put an inline fuse of the appropriate rating or use an IEC socket with a built in fuse holder.

author: peter.mitchell
author_rank: Super Contributor
timestamp: October 20, 2012, 08:54:20 am
content: Usually when I see them hollow pins I tin some wire put it in and solder it, then slide some heat shrink over it and shrink it. I don't know if this is right but it works. I'm not sure what the transformer board is, please include a picture, as usually I would just use a center tapped transformed for the ac-g-ac connection...

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 21, 2012, 09:27:59 am
content: Thanks again Peter!It's this:http://www.savemylight.co.uk/lightingtransformers/get1003160w.htmlJindel 160W Electronic Transformer, brown and blue in, white and grey out, already wired and sealed in a white plastic enclosure with no obvious way to get inside...Come to think of it, the word "Electronic" in the name above probably means its switching the 240v on/off really quickly to get it down to 12v and it may not be suitable.Should I buy something a bit more suitable, happy to do that, this looks like what I need:http://www.ebay.com.au/itm/261019847355Although something a bit more beginner friendly might be good.The guy that sold me the curve tracer and 12-18V AC to +/- 15v DC supply sent me this:http://i237.photobucket.com/albums/ff306/chai_ning/Curve_tracer_Dual_Supply.jpgSo I will have:240v to 12v centre tapped transformer -->> 12-18V AC to +/- 15v DC -->> curve tracerCome to think of it, it would be cool to simply get a supply that did 240v AC to +/- 15v DC, is this possible?/Richard

author: SeanB
author_rank: Super Contributor
timestamp: October 21, 2012, 09:36:09 am
content: 160W electronic transformer means it is a switching power supply, and you probably get the raw 20kHz AC from the transformer on the pins as is, as a lamp does not care about the actual waveform, but integrates it into heat ( and a little light) regardless. Using it as a power supply will lead to a world of not fun, you can never be sure what it will give out, except it will not be nice DC or a nice sine wave. Some give a 100V pulse with a duty cycle that integrates it to 11V RMS. They tend to blow up LED lamps quite well.

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 21, 2012, 09:50:08 am
content: Thanks Sean.OK whats the cheapest and safest way for me to get a 240v AC to +/- 15v DC power supply that I can use with this curve tracer?Thanks all.Richard

author: peter.mitchell
author_rank: Super Contributor
timestamp: October 21, 2012, 10:04:52 am
content: http://www.ebay.com.au/itm/390466269609is the type of transformer you will need, the first transformer you linked isn't suitable for this current application because it doesn't provide 2 AC outputs and because they could be very "dirty", the second transformer isn't suitable, because even though it is a 12.6V transformer, each half will only provide 6.3V AC, much lower than what is required. This transformer provides what you need.Basically,Code:240vac active -> fuse-> (transformer)| -> 12vac -> AC1 in on AC->DC board|-> 0v -> 0v on AC -> DC boardneutral<- | -> 12vac -> AC2 in on AC ->DC boardEarth-----------O connected to metal transformer case + enclosure chassis.You can get a 240v ac to +/- 15v dc but since you have already got the rectifier board and the transformer is only $14 may as well do this.

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 21, 2012, 10:24:23 am
content: Thanks PeterBut if I decided to chicken out would this work?http://www.ebay.com.au/itm/26110794485435W triple voltage output(+12/-12/+5v) power supply.Richard

author: SeanB
author_rank: Super Contributor
timestamp: October 21, 2012, 10:40:13 am
content: Yes, you will get good results from these, but you might find regulation on the 12V rails needs a load on the 5V rail. Normally the 5V rail is the one providing regulation feedback, so most of the draw current wise must come from the 5V rail. Often you can just put a 10W 4R7 resistor across the 5v rail to ensure a minimum load if all that you need is 12V supplies at under 200mA.

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 21, 2012, 11:19:02 am
content: Thanks SeanShould I just get a similar 12v dual output, am I right that one output could be wired to do -12v?Richard

author: SeanB
author_rank: Super Contributor
timestamp: October 21, 2012, 11:22:33 am
content: Yes, probably will work.

author: jeremy
author_rank: Super Contributor
timestamp: October 21, 2012, 11:40:50 am
content: Grab a PSU out of any PC made in the last 10 years, has +-12V as well as a bunch of other voltages. Just short the green wire to ground to switch it on.

author: peter.mitchell
author_rank: Super Contributor
timestamp: October 21, 2012, 12:37:01 pm
content: Quote from: jeremy on October 21, 2012, 11:40:50 amUnfortunately you usually have to do a little cross loading on them so they regulate properly, and the -12 rail is pretty weak usually (500ma MAX, even then they get wobbly), then if you get a cheap one they're pretty noisy and overall probably not what you want.Quote from: rthorntn on October 21, 2012, 11:19:02 amQuote from: SeanB on October 21, 2012, 11:22:33 amJust get the dual output, make sure the outputs are floating/isolated and you'll be fine. Oddly, they all look bloody expensive.A cheap way of getting the power you want would be getting two 12v SLA batteries and a battery charger - no ripple on a batteries outputs

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 21, 2012, 02:19:12 pm
content: Sorry all I messed up, I actually need +15v and -15v...I really am trying to avoid dealing with bare mains transformers and happy to part with $50Richard