H-Bridge

Hy Kal,

kal.a said:

Hi spec, hope you're having a great Sunday

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I had an excellent Sunday thanks- hope you did too. It is mother's day in the UK and our Son and his fiance visited. We had splendid three course lunch and bottle of Merlot at a Bistro owned by some friends and I am feeling fatter than ever. Later I sorted out some hardware problems on a PSU my Son has just bought and he sprinkled some magic dust on my laptop which sorted out some files that I managed to corrupt. Meanwhile the ladies discussed wedding dresses, babies and stuff like that.

kal.a said:

Q35 should not affect how fast Q27 turns on based on where Q32 is placed in the circuit. R24 will get V+ directly through the opto and if we're talking 40V then it will be 39.40V/470Ohms = 83mA and 3.27Watt. (even at 24V+ it's more than 1 Watt)

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Well you certainly know your way around a data sheet kal. You are quite correct- sloppy design by me.

kal.a said:

Also for a 40V+ supply, I will be exceeding the absolute maximum voltage of the Opto detector Vceo of 30V.

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Nice bit of data sheet sleuthing again kal. You have just detected a bit more sloppy design by me. I just looked at the first part of the data sheet and saw 70V max VCE when that was the 'not to exceed without damage VCE' rather than 'operate OK VCE', which is 30V as you say.

kal.a said:

If any of this is correct, I could place R35 higher (before R24) which resolves the current issue and add a resistor to pull down the base of Q27 to turn it off quicker.

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You are on the right lines but there appears to be an error on your schematic in that the input signal for QN1 is connected to 0V.

kal.a said:

But there will still be the issue of exceeding the voltage rating of the opto detector.

For that I could put a voltage divider and everything would look like **broken link removed**but I have concerns about the lack low current in case of 12V+ supply.

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Once more, you are on right lines but the voltage modulation caused by the resistors in the collectors would slow the opto receiving transistors down a bit.

Post #88 shows a revised schematic of the H bridge which I hope takes care of the problems you have highlighted.

Cheers

spec

Wow, busy Sunday. I'm just about to hit the road for a 1200Km drive through the mountains. Should be fun.

kal.a said:

Wow, busy Sunday. I'm just about to hit the road for a 1200Km drive through the mountains. Should be fun.

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Drive sounds great. Do you use Km in Canada- I thought miles, like the UK. Which mountains?
spec

We use KM for distance and inches/feet . Measurements!

I'm driving from Calgary to Vancouver. Starting with the rockies rockies , then numerous BC mountains.

kal.a said:

We use KM for distance and inches/feet . Measurements!

.

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Canada is totally Metric (officially)?
We needed it as we were caught between Imperial and US measure.
At least now it is an International standard.
I still get a 16oz pint when I go to my local pub though!
Max.

It depend on what officially means. Cars have to have Km/h speedometer to get them into Canada but try to buy anything from limber to groceries and. It's feet and pounds.

kal.a said:

It depend on what officially means. Cars have to have Km/h speedometer to get them into Canada but try to buy anything from limber to groceries and. It's feet and pounds.

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No quite, Grocery stores and other types of sales Can show pounds and feet/inches, but by law according to Weights and Measures Canada, the metric equivalent should always be displayed.
It is not always enforced, as in the widespread use of the US pint in the US based restaurants here, I was even in one establishment that advertised the 'House Pint' turned out to be 13ozs.!
IMO Canada Needed Metric, when I came here in '70 I could buy a (US) Gallon of cooking oil but when filling up at the gas pump, it was Imperial Gallon.!
Max.

Hy kal,
Here is a revised schematic of the 12V to 40V H bridge.

(1) I have dropped in an LM317 three terminal voltage regulator to generate a stabilized 9V voltage line for for the opto receiving transistors. I tried out a few other approaches but a voltage regulator is the simplest, cheapest and easiest approach I could find quickly.

(2) You may be wondering why 9V rather than 11V which would have been optimum for the opto receiving transistors, when you take into account the approximately 1V drop in the emitter circuits. The reason is practical: the LM317 voltage regulator has a minimum drop-out voltage of 3V and the minimum H bridge supply line voltage is 12V (12 to 40V) so 12V-3V= 9V.

I could have designed a circuit that would produce 11V from the 12V supply line quite easily, but it would have been more complicated. I could have used a low dropout (LDO) voltage regulator, but they are less common and more expensive, and finding an LDO regulator that would stand a 40V input requires a bit of research.

(3) You may like to investigate a suitable three terminal LDO regulator if you have the time. Go for one with at least 100mA current capacity. Linear Devices, Micrel and Maxim have some good LDO regulators, but you need to ensure that any part you choose, is well behaved, available, cheap, and is going to be available in the future (main line product) or a suitable functional replacement is going to be available in the future. With three terminal voltage regulators you have no worries in this respect because they always will be available, besides which, if push came to shove, you could even roll your own three terminal regulator.

(4) There is a major goof on both of my previous H bridge schematics in that the OV of both the 5V and the H bridge voltage rails are connected. This has been corrected in the ERRATA for both schematics.
ERRATA
(1) 9VV STABILISED RAIL should read 9V STABILISED RAIL. (typo only)
(2) Zener diodes type should read BZX79-18, not BZV18.
(3) R12 should read 1K1 not 1K

NOTES
(1) C6 value, (10 mF) means 10,000 uF
(2) The value of all capacitors in this circuit can be increased provided the same capacitor type is maintained. Normally capacitor types are low frequency decouples (aluminum electrolytics) or high frequency decouplers (ceramic, polycarbonate).
(3) Capacitors can always be wired is parallel to make up a particular value, but they should not be wired is series.
(4) Component tolerances should be +-10% or tighter unless otherwise stated.
(5) D5 can be any 1N400x, where x is 2 or higher or any other rectifier diode with a forward current of 1A or more and a peak inverse voltage (PIV) of 50V or more.
(6) It is advisable, but not essential, to use metal film or tin oxide resistors
(7) All resistors are 500mW unless otherwise stated or calculations show that 250mW will be adequate.
(8) Any 18V 500mW to 1W Zener diode can be used in place of the BZX79-18, for example 1N5249B.
(9) Strictly speaking, the logic gate should be a 7400, 74AS00, or 74S00 to provide at least 10mA current sink for the opto transmitting diodes, but a 74LS00 will be acceptable.

DATA SHEETS
(1) NTE2395 NMOSFET
http://www.nteinc.com/specs/2300to2399/pdf/nte2395.pdf
(2) IRF9540N PMOSFET
http://www.irf.com/product-info/datasheets/data/irf9540ns.pdf
(3) 4N25 Optocoupler
http://www.vishay.com/docs/83725/4n25.pdf
(4) BC546 NBJT
http://www.fairchildsemi.com/datasheets/BC/BC547.pdf
(5) BC556 PBJT
http://www.fairchildsemi.com/datasheets/BC/BC557.pdf
(6) LM317 V Regulator
http://www.ti.com/lit/ds/symlink/lm317.pdf
(7) 74xxx00 TTL Quad two input NAND gate
http://www.ti.com/lit/ds/symlink/sn74ls00.pdf
(8) 1N400x Rectifier Diode
http://www.vishay.com/docs/88503/1n4001.pdf

About units of measurement- we have a similar confusing situation in the UK. Officially we are metric, except where not. Overall the metric system is far better, almost by definition but, from a human point of view, I still prefer imperial units for some things. For example, with fuel, a gallon feels more meaningful than a liter, and a persons height in feet and inches is more intuitive than mm. When centigrade first came in we had a problem getting the feel for what the new figures but, now that we are familiar with degrees C, we find F awkward. Where metric is bad is when you are measuring anything reasonably big, say a garden fence. I find I am always making errors. And on architectural drawing you get measurements like 3658 mm which intuitively means nothing to me, but 12 feet does.

Of course, things get crazy when you get mixtures of measuring standards like at builders merchants and then there is the buggers muddle of the car (auto) tire measurement standard. For example: 255/ 65/ HR/ 17 = mm tread width/ % aspect ratio/ speed rating in MPH/ inch wheel diameter.

kal.a said:

I'm driving from Calgary to Vancouver. Starting with the rockies , then numerous BC mountains.

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Bet you had a great drive with some fantastic scenery. Hope the roads were OK. I understand it can get extremely cold in the mountains this time of year.
I Googled Calgary and was surprised to learn that it is such a vast, thriving, modern city. My impression of it were from mentions in books about the gold rush days in the Yukon.

spec said:

About units of measurement- we have a similar confusing situation in the UK. Officially we are metric, except where not. Overall the metric system is far better, almost by definition but, from a human point of view, I still prefer imperial units for some things.

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How about those Stone's?
(body weight).
Max..

MaxHeadRoom78 said:

How about those Stone's?
(body weight).
Max..

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Ah yes Max,

A weight of 14stone 4lbs (my current weight following the Xmas excesses, but should be 11 stone 7lb) means something but 90.72 Kg means nothing to me.
spec

spec said:

Ah yes Max,

A weight of 14stone 4lbs (my current weight following the Xmas excesses, but should be 11 stone 7lb) means something but 90.72 Kg means nothing to me.
spec

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And how "14 stone 4 lbs" easier to visualize than just saying 200 pounds?

I never had any problem adapting to metric currency over L.S.D. (not the drug).
Although UK switched after I left.!
Max.

gophert said:

And how "14 stone 4 lbs" easier to visualize than just saying 200 pounds?

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It's just what you are used too. I must admit that I could get with Kg quite easily- it's just a rebellion thing really.

MaxHeadRoom78 said:

I never had any problem adapting to metric currency over L.S.D. (not the drug).
Although UK switched after I left.!
Max.

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I welcomed decimal currency big time as soon as it came in- the old £ s & d was a nightmare. I wonder why we can't have decimal time too?

spec said:

. I wonder why we can't have decimal time too?

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Probabally because a large segment of population still insist on wearing 600yr old technology on their wrist!!
I can't remember when I last wore an analogue watch.
Max.

MaxHeadRoom78 said:

Probabally because a large segment of population still insist on wearing 600yr old technology on their wrist!!
I can't remember when I last wore an analogue watch.
Max.

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Oh dear, afraid I am guilty of wearing 600year old technology on my wrist, although I have got a digital watch for doing rough work.

MaxHeadRoom78 said:

Probabally because a large segment of population still insist on wearing 600yr old technology on their wrist!!
I can't remember when I last wore an analogue watch.
Max.

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I keep getting them as gifts. Now my family thinks I collect the damn things. Either that or they are sick and tired of me showing up late to everything. No, I guess they would give me easy-to-read digital watches with alarm if they were pushing the late message - no solid gold case necessary for that.

Barrels are much worse. Not even consistant.