Screwfix Access Control problem

[Mungo Henning]

Hi Folks, My nephew bought the keypad access control "kit" from Screwfix - their part number 27496-77 (page 169 of the most recent catalogue). The locking "strike" seems standard, the keypad takes 12 to 15volts DC and looks "standard", the transformer is one of those with screwholes and a DIN-mounting capability.

Since nephew had some "issues" with wiring the whole lot together, I got a phone call. Eventually I cut my losses and said "just bring it to me and I'll temporarily wire it up then you can take it home and install it proper."

The transformer in the picture (the white cube on the left in the catalogue) is basically just that, with an AC output. Being in the fortunate position to own an oscilloscope, I even double-checked what I saw and watched quite a nice sine wave appear.

When you read all the blurb about the keypad, it states that it needs DC.

So I emailled Screwfix and asked their advice.

The reply I got was: We have supplied many of these items in the past and have not had any queries of this nature.

I would suggest that you contact our supplier, Tate Fire on 01934

744111, and discuss it with them. They are in a much better position to advise you as to compatibility than we are.

I don't want to send 12 volts AC into a unit that takes 12v DC.

I'm thinking that some electrically-ignorant bod has seen that the solenoid lock mechanism can take AC or DC so they have presumed that the electronics can do so too. I haven't looked in depth at the keypad electronics - I suppose I could look for a bridge rectifier on the power side, but I'm guessing there won't be one of these.

So, has anyone else here bought such a unit, and if so how did you get on with it?

I could lash together a rectifier, smoothing capacitor and voltage regulator to give sufficient DC, but having paid ninety quid for the pleasure I think my nephew ought to deserve better.

Feedback requested please; thanks in advance.

Mungo

[Dave Plowman (News)]

If you do it'll be toast. ;-)

[Dave Plowman (News)]

I'd expect it to be marked with the output.

Thinking on it, the solenoid will take the majority of the current, so that might just be AC driven, while the keypad electronics have their own internal rectifier, etc. This would allow a smaller sized enclosure for the power supply - and indeed perhaps only transformers rather than power supplies are available in this DIN fitting type.

[Alan]

In message , Mungo Henning wrote

The data sheets or the specs on the Tate site indicate that the keypads are 10 to 15V dc or 12V ac. They may have a bridge rectifier as the first active component after the input thus allowing both ac and dc.

The transformer shown in Screwfix appears to be the same as the ones shown on the Tate Fire site.

[Mungo Henning]

My sister phoned Tate earlier today and was told that the keypad could tolerate an AC supply. They just haven't got round to updating the instructions... !

Thanks to all who responded.

Mungo

... if all else fails, read the instructions... :-)