VOLTAGE REGULATOR HOT TIP
Discussion
I imagine lots of you have Fuel gauges and Temp Gauges with readings all over the place.
I have found a good fix for them both thanks to a French friend François in Club Lotus France.
Replace the Voltage Regulator from the stone age.
Fit an "adjustable step down converter module LM2596 DC-DC voltage regulator switching".
You can buy these on EBay UK ref: 162289623433 and they are very cheap, peanuts.
They are so cheap you can dedicate one to the Fuel Gauge and a different one for the Temperature Gauge.
Once wired up you can Tune in the reading.
Let me know if you try it and give your opinion
Alan
I have found a good fix for them both thanks to a French friend François in Club Lotus France.
Replace the Voltage Regulator from the stone age.
Fit an "adjustable step down converter module LM2596 DC-DC voltage regulator switching".
You can buy these on EBay UK ref: 162289623433 and they are very cheap, peanuts.
They are so cheap you can dedicate one to the Fuel Gauge and a different one for the Temperature Gauge.
Once wired up you can Tune in the reading.
Let me know if you try it and give your opinion
Alan
That's twice the price and you can't tune it in. What i suggested you can tune in so the readings are spot on. You can adjust the output from 3v upto 35v as you need. So if your Fuel Tank sender is not spot on you can adjust out it's error. Same for the Temperature Sender.
e.g. for the Temp Sender if there is some resistance in the circuit somewhere you simply tune out that problem. You can use an Infra Rouge thermometer and therefore have a Temp Gauge that shows the real temp.
Alan
e.g. for the Temp Sender if there is some resistance in the circuit somewhere you simply tune out that problem. You can use an Infra Rouge thermometer and therefore have a Temp Gauge that shows the real temp.
Alan
....... But a TVR with accurate gauges, no that's just not right 
plasticpig72 said:
That's twice the price and you can't tune it in. What i suggested you can tune in so the readings are spot on. You can adjust the output from 3v upto 35v as you need. So if your Fuel Tank sender is not spot on you can adjust out it's error. Same for the Temperature Sender.
e.g. for the Temp Sender if there is some resistance in the circuit somewhere you simply tune out that problem. You can use an Infra Rouge thermometer and therefore have a Temp Gauge that shows the real temp.
Alan
This may be of help to those thinking about using this very good modificatione.g. for the Temp Sender if there is some resistance in the circuit somewhere you simply tune out that problem. You can use an Infra Rouge thermometer and therefore have a Temp Gauge that shows the real temp.
Alan
It isn't possible to tune out an electrical problem
A fault in an electrical circuit due to a volt drop (high resistance) is not stable, the resistance due to a bad connection or anything else will vary depending upon what current is flowing through the circuit or what voltage is being applied to the circuit and also weather conditions
Faults are for fixing, modifications are for improving. Your modification is very good when used in stable correctly functioning circuits but is of no use when used in a faulty circuit
Edited by Penelope Stopit on Sunday 2nd September 11:55
plasticpig72 said:
+1 soooo cheap and you can put one for each instrument, lots of choice
Alan
So for the temp gauge what is needed to fit this - can it be done without removing the gauge? Alan
I can see that a temp or fuel sender over-reading could be tuned down to bang on but a low reading sender is a sender issue non? You’re clearly up on all this Alan is there an in-line tuneable unit that could be fitted to the sender to gauge wire and adjusted ?
plasticpig72 said:
I don't know between the Sender and the Gauge. The Sender must be the correct one for the Gauge.
Also as Penelope said Circuits must be in good condition.
The idea of using a Voltage Stabiliser with an adjustable output is to maybe have a better reading on the Gauge.
Alan
That's sort of true, but you can (with care) use technically mismatched ones....Also as Penelope said Circuits must be in good condition.
The idea of using a Voltage Stabiliser with an adjustable output is to maybe have a better reading on the Gauge.
Alan
Here's a bit of info which may help.
Lucas/Smiths gauges on most BL family vehicles are 10 volts.
Ford gauges are mostly 5 volts.
So if you say, fit a Ford engine in your car with Smiths gauges, they will read way over the top, as the sensors are designed for 5 volts.
If you can find a Smiths temp sender which fits in your Ford lump (in some cases you can) then it all works out.
If not, you can get a 'sort of' OK gauges by using 7-8 volts (half way between the two), but the scale isn't quite right, so it is compressed at one end,
but you can still set it so that 'N' is in the right place.....but a bit dodgy for a fuel gauge.
But I agree with Penelope, it won't compensate for wiring or earth problems - fix those first.
An electronic regulator DOES however give you more stable readings overall, and can be 'trimmed' to get a perfect 'N' or centered needle reading, and cheap enough
to have one per gauge.
The gauges are 'hot wire' - they just use a little heating element on a bimetal strip to push the needle, so respond only to current flow through them.
NOTE - not all gauges work this way - the Stewart Warner ones in the early wedges don't have ANY regulator , (I guess they are a 'moving coil' type or hybrid)
I know this as putting a regulator on them makes only a tiny difference to their readings. Done that. Putting a resistor in series DOES trim the temp gauge reading though.
Actually in a lot of cases the temp and fuel gauges are interchangeable (i.e. use the same calibration), which can be useful for testing and fault finding....
Edited by RCK974X on Sunday 2nd September 22:56
Thanks Rick for lots of good info.
So if you have a Ford Fuel Gauge you supply it with it's own dedicated Regulator with output adjusted to 5V.
If you have a Smiths Temp Gauge you supply it with it's own dedicated Regulator adjusted to 10V.
For sure if you have the Temp Gauge showing 100°C and the true Temp is 90°C it would be nice that it showed 90°C.
Alan
So if you have a Ford Fuel Gauge you supply it with it's own dedicated Regulator with output adjusted to 5V.
If you have a Smiths Temp Gauge you supply it with it's own dedicated Regulator adjusted to 10V.
For sure if you have the Temp Gauge showing 100°C and the true Temp is 90°C it would be nice that it showed 90°C.
Alan
As I see it (and I don’t like electrics!): The supply to the gauges will be correct ie 12v and whatever is in the gauges will do whatever it does. It’s the sender that’s the issue in sending the wrong voltage to the gauge so a variable resistor could trim that to be correct.
So, do these do that and go onto the sender to gauge wire or do they go elsewhere and if so then is an alternative a variable resistor on said wire to mate the sender to the gauge?
So, do these do that and go onto the sender to gauge wire or do they go elsewhere and if so then is an alternative a variable resistor on said wire to mate the sender to the gauge?
V6 Pushfit said:
As I see it (and I don’t like electrics!): The supply to the gauges will be correct ie 12v and whatever is in the gauges will do whatever it does. It’s the sender that’s the issue in sending the wrong voltage to the gauge so a variable resistor could trim that to be correct.
Not quite. The typical one wire sensors on older cars (e.g. coolant temp or fuel sender) are variable resistors that control current through the gauge rather than sending a voltage, i.e. its a low impedance system. Full scale current is determined by the voltage regulator, and the full scale resistance of the sensor.A switching regulator may not be the best choice in this application, at least not the cheap chinese modules on eBay. Not only do they tend to be a little fragile in terms of handling automotive voltage surges, they also radiate a lot of RF interference (like the cheap cigarette lighter USB chargers). A linear voltage regulator is less efficient, but an extra few hundred millwats of power is hardly a consideration in a car. Sufficient heat sinking will be required to keep the regulator temperature reasonable however.
Edited by Mr2Mike on Monday 3rd September 07:17
From those responses, I see some of you could do with a bit more on how the gauges work....
A simple guide...(don't panic - I will keep it simple !!).
The senders (fuel and temp) are effectively nothing more than a variable resistor. (just like the dimmer for the dash lights)
The gauges respond to current (amps) flowing through them. More amps = higher reading.
Ford numbers aren't quite half of the Smiths number as I remember, but roughly true more or less ...
The following numbers may help (Smiths)
The simple rule for current flow through something is Amps = Volts/Resistance, so the std gauge needs a constant voltage (and alternators/dynamos are NOT !!).
So you need a voltage regulator.
The Smiths gauge is typically about 60 ohms.
The Smiths temp senders vary from about 2500 ohms cold, to 60 ohms 'normal' to about 25 ohms full scale hot. (for all of them as far as I know)
Fuel is the same - senders go from about 2500ohms empty to about 25-35 ohms full.
So full scale reading on a Smiths gauge is approx 10/(25+60) [Volts/total resistance] = 110 milliamps (or 0.110 amps)
normal 'N'/ centre = 10/(60+60) = 83 milliamps
and to read at all they need about about 15 milliamps (from memory), so that sender value ensures they don't read at all when cold.
If you add a resistor to compensate for a high reading, it squashes the top end more than the bottom -
e.g. add a 15 ohm resistor...
Cold 2500+15 hardly any difference < 1% change
Normal 60+15 noticeably lower 25% change
Hot 25+15 a LOT lower >50% change
With a Ford sender - if it's half ohms values for 5 volts, then it goes from 1200ohms to about 15ohms , so your 'N' on
a Ford sender with Smiths gauge gives 10/(30+60) and gauge goes to full scale or hits the stop at full HOT. e.g. For 10 volts .. (10/90 = 110 milliamps).
Dropping to 7.5 volts would work for 'N' in this example as 7.5/(30+60) = 83 milliamps,
but HOT then gives 7.5/(15+60) = 100 milliamps ... a bit low for HOT, but probably good enough to keep an eye on.....
You can do this on a spreadsheet and play with it, and you can measure resistances and current flows with a cheap multi meter.
This also shows that you don't need much of a dodgy earth to start affecting the gauge readings....
I hope that helps everyone....
A simple guide...(don't panic - I will keep it simple !!).
The senders (fuel and temp) are effectively nothing more than a variable resistor. (just like the dimmer for the dash lights)
The gauges respond to current (amps) flowing through them. More amps = higher reading.
Ford numbers aren't quite half of the Smiths number as I remember, but roughly true more or less ...
The following numbers may help (Smiths)
The simple rule for current flow through something is Amps = Volts/Resistance, so the std gauge needs a constant voltage (and alternators/dynamos are NOT !!).
So you need a voltage regulator.
The Smiths gauge is typically about 60 ohms.
The Smiths temp senders vary from about 2500 ohms cold, to 60 ohms 'normal' to about 25 ohms full scale hot. (for all of them as far as I know)
Fuel is the same - senders go from about 2500ohms empty to about 25-35 ohms full.
So full scale reading on a Smiths gauge is approx 10/(25+60) [Volts/total resistance] = 110 milliamps (or 0.110 amps)
normal 'N'/ centre = 10/(60+60) = 83 milliamps
and to read at all they need about about 15 milliamps (from memory), so that sender value ensures they don't read at all when cold.
If you add a resistor to compensate for a high reading, it squashes the top end more than the bottom -
e.g. add a 15 ohm resistor...
Cold 2500+15 hardly any difference < 1% change
Normal 60+15 noticeably lower 25% change
Hot 25+15 a LOT lower >50% change
With a Ford sender - if it's half ohms values for 5 volts, then it goes from 1200ohms to about 15ohms , so your 'N' on
a Ford sender with Smiths gauge gives 10/(30+60) and gauge goes to full scale or hits the stop at full HOT. e.g. For 10 volts .. (10/90 = 110 milliamps).
Dropping to 7.5 volts would work for 'N' in this example as 7.5/(30+60) = 83 milliamps,
but HOT then gives 7.5/(15+60) = 100 milliamps ... a bit low for HOT, but probably good enough to keep an eye on.....
You can do this on a spreadsheet and play with it, and you can measure resistances and current flows with a cheap multi meter.
This also shows that you don't need much of a dodgy earth to start affecting the gauge readings....
I hope that helps everyone....
https://www.ebay.co.uk/itm/LM2596-DC-DC-Switching-...
Features:
Conversion efficiency: Up to 92% (the higher the output voltage, the higher the efficiency)
Potentiometer adjustment direction: Clockwise (increase), Anti-clockwise (decrease)
Switching frequency: 150KHz
Rectifier: Non-synchronous rectification
Module properties: Non-isolated step-down module
Short circuit protection: Current limiting, self-recovery
Operating temperature: Industrial grade (-40 to +85 degrees Celsius) (output power 10W or less)
Load regulation: +/- 0.5%
Voltage regulation: +/- 2.5%
Dynamic response speed: 5% 200uS
Connection mode: Welded, plus pin can be directly soldered PCB
Specifications:
Input voltage: 3-40V
Output voltage: 1.5-35V (adjustable)
Output current: Rated current is 2A, maximum 3A (if the output power more than 10W, the heat sink is needed.)
Item size: 48 * 22 * 12mm / 1.9 * 0.9 * 0.5in
Item weight: 12g / 0.4oz
Something that needs checking out with this is.....If the input voltage increases does the output voltage increase, decrease or remain as adjusted to
There could be a problem if the regulator is adjusted when the input voltage is approx 12 volts yet that voltage is 14 to 14.5 volts when the alternator is running and charging
If the above is the case then some users may prefer to adjust the regulator when the alternator is running and charging
Someone that knows more about the regulators characteristics may visit here and add to this
Features:
Conversion efficiency: Up to 92% (the higher the output voltage, the higher the efficiency)
Potentiometer adjustment direction: Clockwise (increase), Anti-clockwise (decrease)
Switching frequency: 150KHz
Rectifier: Non-synchronous rectification
Module properties: Non-isolated step-down module
Short circuit protection: Current limiting, self-recovery
Operating temperature: Industrial grade (-40 to +85 degrees Celsius) (output power 10W or less)
Load regulation: +/- 0.5%
Voltage regulation: +/- 2.5%
Dynamic response speed: 5% 200uS
Connection mode: Welded, plus pin can be directly soldered PCB
Specifications:
Input voltage: 3-40V
Output voltage: 1.5-35V (adjustable)
Output current: Rated current is 2A, maximum 3A (if the output power more than 10W, the heat sink is needed.)
Item size: 48 * 22 * 12mm / 1.9 * 0.9 * 0.5in
Item weight: 12g / 0.4oz
Something that needs checking out with this is.....If the input voltage increases does the output voltage increase, decrease or remain as adjusted to
There could be a problem if the regulator is adjusted when the input voltage is approx 12 volts yet that voltage is 14 to 14.5 volts when the alternator is running and charging
If the above is the case then some users may prefer to adjust the regulator when the alternator is running and charging
Someone that knows more about the regulators characteristics may visit here and add to this
Penelope Stopit said:
Something that needs checking out with this is.....If the input voltage increases does the output voltage increase, decrease or remain as adjusted to
It's a voltage regulator, it's entire purpose in life is to maintain a stable output voltage. There will be some small change with input voltage (line regulation) and output current (load regulation) and some change over temperature, but these effects should be miniscule (for an automotive application) for a half decent regulator.Again there is a risk of cheap switching regulator modules causing interference with radios etc.
Edited by Mr2Mike on Tuesday 4th September 10:18
Further to my above post, having checked the information given at this website (found randomly and many may differ),
https://www.cableworks.gr/ilektronika/arduino-and-...
the input voltage must be greater than the output voltage to 1.5V or more
Bearing in mind that specifications may well vary from manufacturer to manufacturer -
There is a possible show stopper here
As an example - Anyone that is getting 12.5 to 13 volts at the battery which is often the case when the alternator is at full output and the vehicles headlights and blower plus a n other are on are going to be restricted to a maximum output voltage of 11 volts
This very good modification will be very good for some yet inadequate for others. Calculations need to be made before making a decision on whether this modification is a goer or a noer
https://www.cableworks.gr/ilektronika/arduino-and-...
the input voltage must be greater than the output voltage to 1.5V or more
Bearing in mind that specifications may well vary from manufacturer to manufacturer -
There is a possible show stopper here
As an example - Anyone that is getting 12.5 to 13 volts at the battery which is often the case when the alternator is at full output and the vehicles headlights and blower plus a n other are on are going to be restricted to a maximum output voltage of 11 volts
This very good modification will be very good for some yet inadequate for others. Calculations need to be made before making a decision on whether this modification is a goer or a noer
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