Electronics Hardcore pump powersupply project questions

Hi all, I'm new to electronics but got some basic knowledge, new to this forum as well.

I've got a D4 pump and want to build a seperate powersupply for it. I've been running the D4 off my nexus fan controller and it only suppply up to 12V. However, the D4 is rated for 6-24V. Therefore, i want to build a seperate powersupply to make full use of the power.

My plan is building a mains powersupply with voltage control wired up to a relay and an on-the-fly voltage reading on a LCD

Transformer:

I'm planning to use the 100VA mains transformer kit from maplin (quickfind: YJ63T)

Voltage regulating circuit:



Relay:



However, I'm not sure what diode and what relay to use. I'm not even sure if the diode is necessary as I'm connecting it to a transformer.

I'm looking at quickfin: JM67X from maplin for the relay but not sure if it's the right one as there's not much information about it.

Voltage meter circuit:

Now, I have absolutely no idea what to get for this. I've been looking at http://kitsrus.com/projects/k127.pdf. Is this what I should be looking at? Also, can I get the seperate parts from maplin?

Also, I want to switch between monitoring the pump voltage and a few other voltages in the system as I have quite a few voltmods in the system. I'm sure a simple switch can do the trick though.

The pump will be drawing about 5A. Would it be a problem to do all these on a stripboard?

 

I've got a OASE 24V pump and I 'm usign a 12/24V step-up convertor.
http://www.m-99.co.uk/Electrical/12v_Car_to_24v_Stepup_Converte/12v_car_to_24v_stepup_converte.html
(but available for pug at www.wizd.co.uk at a better rate afaik - I got mine there with the pump)

It provides 12-24V switchable from your 12V PSU.

I'd be interested in a better solution if you can find one. In particular anything that would be continuously adjustable from the front panel.

I was looking the other day and saw the LM2577 Step-Up Voltage Regulator (Maplin AD90X) which might do the job (its rated for the voltages to 60V out) but the examples are only for 12V from a 5V supply). If that could be adapted it would be tidier than another transformer.

However looking at the pump specs http://www.dangerden.com/images/pumps/12v/dd12v_power_lg.jpg yours draws 3A at 21V so you're a bit high on the spec there.

Maybe there are some alternate parts available?

 

I think a seperate transformer is a better idea for me.

If I do that, I'll be putting an extra 70W on the PSU. Although it is an enermax 550W, I already have a 172W pelt running off it. I don't think having an extra 70W of load is a good idea as my system is seriously overclocked.

Also, I think it's always good to overspec than underspec.... i think 3A wouldn't be quite enough as I'm going up to 24V.

The question is if a stiripboard can take just over 3A.

Any idea about what diode to use in the relay?

 

Use that circuit and there'll be an almighty bang when you turn on. The output is short-circuit.

 

Is it better now?

I think I'm going to buy one of thesehttp://www.electronic-kits-and-projects.com/kit-files/3000/3127.pdf for the on-the-fly voltage reading. However, it uses a 9V battery for power... I want to supply this through the PSU, do I need another regulating circuit or is there something else I can do about it?

 

The idea for a separate PSU is OK but I strongly advice to NOT run the D4 @ 24V...

The rated voltage of the D4 is still 12V, the 6-24V are the absolute minimum/maximum ratings given by Laing, meaning that the pump will not burn out till 24V, not meaning that you can run the pump continuously at that voltage...
The 6V is the minimum start voltage of the D4.

You should not exceed 16V if you want a reasonable MTBF.
At this voltage it draws a little more than 2A maximum.

The 16VDC can be easily obtained from a 12VAC bridge or double phase rectified transformer without the need of a regulator (a 50VA toroidal transformer would be ideal).

When a variable output is needed the 3A MIC29302BT LDO (low drop output) regulator is perfect.
It has even an enable input to switch the regulator output with the computer's PSU, no need for a relay.

The following is a schematic I made when I was using my Johnson 12VDC pumps:

The output is set by P2 from approx. 6 to 15VDC (min/max is set by P1).
Depending from the transformer output voltage a max output up to 16-17V can be obtained.
The regulator is switched by the computer's PSU but this can be bypassed by switch S2.
The MIC29302BT must be cooled by an appropriate heatsink.

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This is very nice indeed

I'll go and get the parts tomorrow.

Just a few more questions before getting the soldering iron out.

1. I'd like a little over 16V, what do you recommend me to set the output voltage of the transformer to? I'm thinking about 18VAC.

2. Can I have a formula to calculate the output voltage to the pump so I know what value I want to set P1 and P2 to?

3. Can a P600D be used instead of a 6A6, maplin don't do 6A6

Thanks very much for everyone's help

 

To get 18V you'll need a 2x15V transformer. Max voltage is then 15 x 1.414 = 21.2V less a volt lost across 1 rectifier diode, 2V loss if you use a bridge rectifier, so 19-20V into the regulator.

Output voltage is 1.25 x (1 + R2/R1) where R2 is the total of the two pots.

If you make R1 10k, so with P1 set at 40k,

P2 at 0, Output = 1.25 x (1 + 40k/10k) = 6.25V

P2 at 100k, output = 1.25 x (1 + 140k/10k) = 18.75V

Don't skimp on the rectifier rating, if the pump averages 2A use at least 5A rectifiers, better still 8-10A

I'd personally go for Maplin's 25A bridge AR84F, not much more than the 2 6A diodes, easier to keep cool and makes more efficient use of the transformer.

 

1. I wasn't really thinking of a higher voltage output transformer, but morely that most transformers put out already a 10-20% higher voltage than their rated voltage (depends also on the wattage of the transformer), so probably you will obtain 19V rectified with a 12V one (the MIC29302 has only a dropout voltage of about 0.35V).

2. Cpemma answered this one.

3. Yes, the 6A6 is a cheap 6A-600V rectifier diode, the P600D is 6A-200V.

Remember, the MIC29302BT is not a cheap regulator (5.88£ at RS - ref. 217-4989).
Does even exist in 5A (MIC29502BT) and 7.5A version (MIC29752BT).

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Indeed perfect for a single secondary transformer, for a dual secondary transformer two diodes do double wave rectifying too.

You could use only two diodes of the AR84F too: 2x12V to the AC connections, rectified output from the + connection, 0V from the center tap of the transformer.

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Just bought some of the parts.

Unfortunately, maplin don't do 50VA transformers anymore and they don't do the regulator. So I bought those from rapidelectronics instead.

I bought the 50VA transformer with 20V output and the MIC29502BT (5A version just in case). Rapidelectronics sell the MIC29302BT for £3.62btw.

However, I'm not sure if I bought the correct transformer because it says 0-20V @ 1.2A It's from rapidelectronics order code: 88-0415

Just need to go to maplin after work and get the rest of the parts now.

 

The MIC29502 is fine but the 20V output of the transformer is way too high (BTW, it's a 2x20V-2x1.2A=2.4A transformer).

20V*1.4-1V= about 27V rectified.
Your MIC will have to dissapate about (27V-18V)*2.3A=18.9W @18V output, and (27V-6V)*0.6A=12.6W @6V, so the heatsink has to be very massive.
It defeats a bit the use of a LDO regulator that needs only 0.5 to 1V more at his input than the output voltage...

2x12V-2x2A (88-0305) or 2x15V-2x1.6A (88-0310) would suite better.
I also advise a toroidal transformer for the reasons enumerated here (ref 88-2618 or 88-2620).

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Don't know if I should praise them or not... I put in the order at around 10:30 and they've already shipped it.... Lesson of the day, always read the post carefully

I'll have to order a toroidal 2X15V and use the 20V one as a paper weight....

 

I have lots of paper weights....

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Here's the theory behind why I said it was less efficient.

With 2 x 12V dual-secondary transformers you can parallel the secondaries & use a bridge. With a 12-0-12 centre-tap you're stuck with the two diodes rectifier unless you want the full 24V.

 

Would it be possible to use the -12 VDC, the blue wire on the ATX connector, as a ground to get you 24 VDC (with splicing inside the PSU of course (not always an option I realize))? Wouldn't the voltage from the yellow with respect to blue be 24, or is that now how it works when you go into negatives in DC?

 

You're right Emon, +12v and -12v negative would net +24v effective. However, the first post said that the pump draws 5A. The -12v line on power supplies is fairly weak. My power supply has a 1A max on that rail (450w), and it's not likely to get that much higher the bigger the power supply you use. Hence the need for a seperate PSU for the pump.

 

I was thinking something along those lines, thanks for filling me in.

 

Turbokeu, I gotta know, what program did you use to generate that schematic?

 

Good link, some lecture for this evening....
I don't like paralleling secondaries because of the inevitable differences in output voltage and the correspondent currents between the secondaries .

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